CHAPTER VII.

 THE ELEMENTARY STRUCTURE OF THE NERVOUS SYSTEM.

 

112. The progress of science involves an ever-increasing Analysis. Investigation¹ is more and more directed towards the separated details of the phenomena² previously³ studied as events; the observed facts are resolved into their component⁴ factors, complex wholes into their simpler elements, the organism into organs and tissues. But while the analytical⁵ process is thus indispensable, it is, as I have often to insist, beset⁶ with an attendant danger, namely, that in drawing the attention away from one group of factors to fix it exclusively on another, there is a tendency to forget this artifice⁷, and instead of restoring the factors provisionally left out of account, we attempt a reconstruction⁸ in oblivion of these omitted factors. Hence, instead of studying the properties of a tissue in all the elements of that tissue, and the functions of an organ in the anatomical connections of that organ, a single element of the tissue is made to replace the whole, and very soon the function of the organ is assigned to this particular element. The “superstition⁹ of the nerve-cell” is a striking illustration. The cell has usurped¹⁰ the place of the tissue, and has come to be credited with central functions; so that wherever anatomists have detected ganglionic cells, physiologists¹² have not hesitated to place central functions. By such interpretations¹⁴ the heart and intestines¹⁶, the glands¹⁹ and blood-vessels²⁰, have, erroneously, I think, their actions assigned to ganglionic cells.

252 It is unnecessary to point out the radical²¹ misconception which thus vitiates a great mass of anatomical exposition and physiological²² speculation²³. I only call the reader’s attention to the point at the outset of the brief survey we have now to make of what is known respecting the elementary structure of the nervous system.

DIFFICULTIES OF THE INVESTIGATION.

 

113. So great and manifold are the difficulties of the search, that although hundreds of patient observers have during the last forty years been incessantly²⁴ occupied with the elementary structure of the nervous system, very little has been finally established. Indeed, we may still repeat Lotze’s sarcasm²⁵, that “microscopic²⁶ theories have an average of five years’ duration.” This need not damp our ardor²⁷, though it ought to check a too precipitate²⁸ confidence. Nothing at the present moment needs more recognition by the student than that the statements confidently repeated in text-books and monographs²⁹ are very often for the most part only ingenious guesses, in which Observation is to Imagination what the bread was to the sack in Falstaff’s tavern³⁰ bill. Medical men and psychologists ought to be warned against founding theories of disease, or of mental processes, on such very insecure bases; and physiological students will do well to remember the large admixture of Hypothesis which every description of the nervous system now contains. Not that the potent³¹ aid of Hypothesis is to be undervalued; but its limits must be defined. It may be used as a finger-post, not as a foundation. It may suggest a direction in which truth may be sought; it cannot take the place of Observation. It may link together scattered³² facts; it must not take the place of a fact. We are glad of corks³³ until we have learned to swim. We are glad of a suggestion which will for the nonce fill up the gaps left by observation,253 and hold the facts intelligibly³⁴ together. And both as suggestion and colligation, Hypothesis is indispensable. Indeed, every discovery is a verified hypothesis; and there is no discovery until verification has been gained: up to this point it was a guess, which might have been erroneous—a torchbearer sent out to look for a missing child in one direction, while the child was wandering in another; only when he finds the child can we acknowledge that the torchbearer pursued the right path. Hypothesis satisfies the intellectual need of an explanation, but we must be wary³⁵ lest we accept this fulfilment of a need as equivalent to an enlargement of knowledge; we must not accept explanation as demonstration³⁶, and suppose that because we can form a mental picture of the possible stages of an event, therefore this picture represents the actual stages. Let us be alert, forewarned against the tendency to seek evidence in support of a conclusion, instead of seeking to unfold the conclusion step by step from the evidence. To seek for evidence in support of a guess is very different from seeking it in support of a conclusion; which latter practice is like that of people asking advice, and only following it when it chimes in with their desires.

114. Is not the warning needed, when we find anatomists guided by certain “physiological postulates³⁸,” and consequently seeing only what these postulates demand? For example, there is the postulate³⁹ of “isolated⁴⁰ conduction,” which is said to require that every nerve-fibre should pursue its course singly from centre to periphery⁴¹. Accordingly the fibres are described as unbranched. Whatever may be the demand of the postulate, or the felt necessity of the deduction⁴², the fact is that nerve-fibres do branch off during their course at various points; nay⁴³, it is doubtful whether any lengthy⁴⁴ fibre is unbranched. Other postulates demand what fact plainly254 denies. It is said to be “necessary” that every cell should have at least two fibres, and that sensory⁴⁵ and motor nerves should be directly connected through their respective cells. These things cannot be seen, but they are described with unhesitating precision. Diagrams are published in which the sensory fibres pass into the cells of the posterior horn of the spinal⁴⁶ cord, and these cells send off prolongations to the cells of the anterior⁴⁷ horn, and thence the motor fibres pass out to the muscles: an absolutely impossible arrangement, according to our present data! Again, the postulate that nerve-force originates in the cells, and that nerve-functions depend on cells, required that the cells should be most abundant where the function was most energetic. Of course they were found most abundant in the required places—no notice whatever being taken of the facts which directly contradicted the deduction.

115. Among the serious obstacles to research we must reckon this tendency to substitute Imaginary Anatomy⁴⁸ for Objective Anatomy. I am conscious of the tendency in myself, as I note it in others; and have constantly to struggle against it, though not perhaps always aware of it. Many a time have I had to relinquish⁴⁹ plausible⁵⁰ explanations, which would have supported my speculations⁵¹ could I but have believed that they represented the facts; but being unable to believe this, I had to remember that hypotheses and explanations appear and disappear—only the solid fact lives. If there is one lesson emphatically taught by Philosophy, it is the unwisdom of founding our conclusions on our desires rather than on the objective facts.

116. In the following pages a constantly critical attitude is preserved: this is simply to keep active the sense of how much is still needed to be done before a satisfactory theory of the nervous system can be worked out.255 The objective difficulties are greater than in any other department of Anatomy. The problem is to form a precise picture of what the organites are, and of how they are arranged in the living tissue; yet our present means of investigation involve as a preliminary that we should alter that arrangement, removing some elements of the tissue, and changing the state of others, without knowing what were their precise state and arrangement before the change. Place a piece of nerve-tissue under the microscope, without having subjected it to various mechanical and chemical operations, and you can see next to nothing of its structure. You must tear the parts asunder⁵², and remove the fat and nerve-sap (plasmode) before you can see anything; you must coagulate the albumen, and otherwise chemically alter the substances before a thin section can be made; you must get rid of the tissues in which it is embedded⁵³, without knowing what are the connections thus destroyed. Living neurine has no greater consistence than cream, often no greater than oil. How, then, can thin sections be made until this viscid substance has been hardened by alcohol or acids? But substances thus acted on lose their constituent⁵⁴ water, which can no more be removed without alteration⁵⁵ of their structure, than it can be removed from certain salts without destruction of their special properties. Losing their water alone, they become deformed⁵⁶. They lose much more. Sometimes the loss can be estimated, as in the case of the hyaline substance investing the nucleus⁵⁷ during the process of segmentation in embryonic⁵⁹ cells, which may be seen to disappear when a weak solution of acid is applied⁶⁰.137 At other times we are unable to say what has disappeared. Under different modes of preparation very different appearances are observed, and anatomists are accordingly at variance⁶¹. Yet unless some hardening256 method be adopted little can be seen! Stilling, who has given his life to the study, declares that no results are reliable which are obtained from the unprepared tissue, because the mechanical isolation⁶² of the elements destroys the textural⁶³ arrangement.138 There is one method of hardening, and only one, which we can be certain does not chemically alter the structure, and that is the freezing method. The experiments of Dr. Weir⁶⁵ Mitchell and Dr. Richardson prove this, because they prove that the brain of the living animal may be frozen and frozen again and again, yet recover its vital activity when thawed⁶⁶. Professor Rutherford has invented an admirable instrument for making sections of the frozen tissue, of any delicacy⁶⁷ that may be required; but with the thinnest section there will still be certain difficulties of observation, unless the tissue has undergone a staining process. Whatever is seen, however, in the frozen tissue is to be accepted as normal.

117. Two points must be determined⁶⁸ before reliance can be placed on observations of tissues chemically acted on: First, we must prove that the forms now visible existed before the preparation—the chemical action merely unveiling them; secondly⁷⁰, we must estimate the part played by the elements which have been removed in order to make the rest visible. We know, for example, that the nucleus often exists in the cell, though an acid may be needed to make it visible. We also know that cells which during life are quite free from visible granules are distinctly granulated after death, even without external chemical action. Imagine the explanation of a steam-engine to be attempted by first taking it to pieces, and examining these pieces, with no account of the coals and steam which had previously been removed in order to facilitate the examination. When we know the part257 played by coals and steam, we may disregard these items of the active machine. So when we know the part played by water, fat, amorphous⁷¹ substance, and plasmode, we may describe nerve-tissue without taking these into account.

118. “You have convinced me,” said Rasselas to Imlac, “that it is impossible to be a poet.” My readers may, perhaps, infer from this enumeration⁷² of the difficulties that a knowledge of the minute anatomy of the nervous system is impossible. Not so; but a knowledge of these difficulties should impress us with the necessity for a vigilant⁷³ scepticism, and the search after new methods. If the difficulties are fairly faced, they may be finally overcome. What we must resign ourselves to at present is the conviction that our knowledge is not sufficiently⁷⁴ accurate to be employed as a basis of deduction in the explanation of physiological and psychological processes.139

119. Having said so much, let me add that there are some positive materials, and these yearly receive additions. The organites are described with a general agreement as to their composition and structure—although there is much that is hypothetical even here. Neurine is known under two aspects: the amorphous and the figured. The figured, which is the better known, comprises cells of different kinds, fibres and fibrils. The amorphous, more generally called Neuroglia, or nerve-cement, is less understood, and is indeed by many authorities excluded altogether from the nerve-tissue proper, and relegated⁷⁶ to the class of connective tissues.

258

THE NERVE-CELL.

 

120. It is unfortunate that the term nerve-cell is applied to organites of very variable structure. Nerve-cell is a generic⁷⁷ term of which the species are many; under it are designated organites in different stages—as infancy⁷⁸, childhood, and manhood are all included under Man. Most commonly by nerve-cell is understood the ganglionic corpuscle, conspicuous⁷⁹ in its size and its prolongations, such as it appears in the great centres, and in ganglia. It also designates smaller different organites, sometimes called “nuclei⁸⁰” (Kerne), sometimes grains (K?rner). There would be advantage in designating the earlier stages as neuroblasts, reserving the word cells for the more developed forms. Such a distinction would facilitate the discussion of whether nerve-fibres had or had not their origin in cells; because while I, for one, see very coercive evidence against the accepted notion that all the fibres have their origin in the processes of ganglionic corpuscles, I see no reason to doubt that both fibres and corpuscles have their origin in neuroblasts. Of this anon.

The cell is a composite organite, the primary element being a microscopic mass of protoplasm, or what may more conveniently be termed neuroplasm. It appears as finely granulated and striated⁸¹ or fibrillated substance on a hyaline ground, with water, fat, and diffused⁸² pigment⁸³ in varying quantities. The cell contains a nucleus, and nucleolus—sometimes two. Like other animal cells, it sometimes has a distinct cell-wall, sometimes not. Its size and shape are variable: sometimes distinctly visible to the naked eye, generally visible only under the microscope.140 It is round, oval, pyramidal, club-shaped, pear-shaped,259 or many-cornered. It has one, two, three, or many outgrowths called “processes,” and according to the processes it is known as unipolar, bipolar, and multipolar. When there are no processes the cell is called apolar. Some idea of these processes may be formed if they are likened to the pseudopodia of Am?b? and Foraminifera.261 Compare Fig⁷⁵. 16, a nerve-cell, figured by Gerlach, with Fig. 17, one highly magnified, in which Max Schultze’s hypothesis is represented.

 

Fig. 16.—Nerve-cell from anterior horn of spinal cord (man), magnified 150 diameters. a, cell process unbranched passing into or joining an axis⁸⁴ cylinder⁸⁵, the other processes are branched; b, pigment. The nucleus and nucleolus are visible.

 

Fig. 17.—Nerve-cell from the anterior gray substance of the spinal cord of a calf⁸⁶ magnified 600. a, the axis cylinder; b, the branched process. The neuroplasm is represented as distinctly fibrillated, with granular substance interspersed⁸⁷. Nucleus and nucleolus very distinct.

121. Such is a general description of the nerve-cell as it is seen in various places, and under various modes of preparation. How much is due to preparation we cannot positively⁸⁸ say. While we always discover fibrine in the blood after it is withdrawn⁸⁹ from the vessels, we know that fibrine as such does not exist in the circulating blood. And if neurine is a semi-liquid substance, we may doubt whether in the living cell it is fibrillated. Doubts have been thrown even on the normal existence of the granular substance, which has been attributed to coagulation⁹¹. Thus we know that the nucleus of the white blood-corpuscle appears perfectly⁹² homogeneous until subjected to heat, yet at a certain temperature (86° F.) it assumes the aspect of a fine network. Haeckel observed the hyaline substance of the neurine in crayfish become troubled and changed directly any fluid except its own blood-serum⁹³ came in contact with it. Leydig noticed the transparent⁹⁴ ganglion of a living Daphnia become darker and darker as the animal died; and I saw something like this, after prolonged struggles of a Daphnia to escape from a thread in which its leg was entangled⁹⁵. Charles Robin⁹⁶, indeed, asserts that the passage from the hyaline to the finely granulated state is a characteristic of the dying cell.141 On262 the other hand, it should be noted⁹⁷ that Max Schultze describes a fibrillated appearance in cells just removed from the living animal, and placed in serum.

When, therefore, one observer describes the neuroplasm as being clear as water, another as finely granular, and a third as fibrillated, we must conclude that the observations refer to cells, 1°, under different states of vitalization, or, 2°, under different modes of preparation. On the first head we note that some nerve-cells are so perishable⁹⁸ that Trinchese declares he could find no cells in the ganglia of a cuttlefish⁹⁹ which had been dead twenty-four hours, although they were abundant in one recently killed.142 On the second head we note that the changes wrought¹⁰⁰ by modes of preparation cannot be left out of consideration. Auerbach notices that the cells and fibres apparent in the plexus myentericus after an acid has been applied, cannot be detected before that application—nothing is visible but a pale gelatinous network, with here and there knots of a paler hue¹⁰¹; and I remember my surprise on examining the fresh spinal cord of a duck-embryo⁵⁸, and finding no trace of cells such as I had that very morning seen in the cord of a chick of earlier date, but which had been soaked in weak bichromate of potash. Now we have excellent grounds for believing that in both cases these organites were present, and that it was the reagent which disclosed their presence in the chick; and so in other cases we must ask whether the forms which appear under a given mode of preparation are simply unmasked, or are in truth produced by the reagent? This question we can rarely answer.

263 If one of the very large cells be taken from the ganglion of a living mollusc, and be gently pressed till it bursts, the discharged contents will be seen to be of a hyaline viscid substance, with fine granules but no trace of fibres. Yet we must not rashly generalize from this, and declare that in the vertebrate cells the substance is not also fibrillated. As a good deal of speculation rests on the assumption of the fibrillated cell-contents, I have thought it worth while to note the uncertainty¹⁰² which hovers¹⁰³ round it.

122. Among the uncertainties¹⁰⁴ must be reckoned the question as to the cell-processes. The existence of apolar and unipolar cells is flatly denied by many writers, who assert that the appearances are due to the fragility of the processes. Fragile the processes are, and evidence of their having been broken off meet us in every preparation; but the denial of apolar and unipolar cells seems to me only an example of the tendency to substitute hypothesis for observation (§ 114). The “postulate” which some seem to regard as a “necessity of thought” that every nerve-cell shall have at least two fibres, one ingoing, the other outgoing, is allowed to override¹⁰⁵ the plain evidence.143 It originated in the fact first noticed by Wagner and Charles Robin that certain cells in the spinal ganglia of fishes are bipolar. The fact was rapidly generalized, in spite of its not being verified in other places; the generalization¹⁰⁶ was accepted because (by a strange process of reasoning running counter to all physiological knowledge) it was thought to furnish an elementary illustration of the reflex process. As the centre had its ingoing and outgoing nerve, so the cell was held to be a centre “writ small,”264 and required its two fibres, No one paused to ask, how a cell placed in the track of an ingoing nerve could fulfil this office of a reflex centre; no one supposed that the portion of the sensory fibre which continued its course, after the interruption of the cell, was a motor fibre.

What does Observation teach? It teaches that at first all nerve-cells are apolar. Even in the cortex of the cerebrum, where (unless we include the nuclei and grain-like corpuscles under cells) all the cells are finally multipolar, there is not one which has a process, up to the seventh or eighth day of incubation (in the chick); from that day, and onwards, cells with one process appear; later on, cells with two, and later still, with three. By this time all the apolar cells have disappeared. They may therefore be regarded as cells in their infancy. However that may be, we must accept the fact that apolar cells exist; whether they can co-operate in neural¹⁰⁷ functions, is a question which must be decided¹⁰⁸ after the mode of operation of cells is placed beyond a doubt.

123. If apolar cells are embryonic forms of cells which afterwards become multipolar, this interpretation¹⁵ will not suffice for the unipolar cells. They are not only abundant, but are mature forms in some organs, and in some animals; though in some organs they may truly be regarded as embryonic. Thus in the human embryo up to the fourth month all the cells of the spinal cord are said to be unipolar,144 later on they become multipolar. But in birds, rabbits, dogs, and even man, the cells in the spinal ganglia are mainly (if not wholly) unipolar;145 nor is there265 any difficulty in observing the same fact in the ?sophageal ganglia of molluscs (see Fig. 22).

Such are the observations. They have indeed been forced into agreement with the bipolar postulate, by the assumption that the single process branches into two, one afferent, the other efferent.146 But before making observation thus pliant¹⁰⁹ to suit hypothesis, it would be well to look more closely into the evidence for the hypothesis itself. For my own part, I fail to see the justification¹¹⁰ of the postulate; whereas the existence of unipolar cells is an observation which has been amply verified.

 

Fig. 18.—Supposed union of two nerve-cells and a fibre. The processes subdivide¹¹¹ into a minute network, in which the fibre also loses itself.

124. Bipolar cells abound¹¹²; multipolar cells are still more abundant; and these are the cells found in the gray substance of the neural axis. Deiters, in his epoch-making work,147 propounded¹¹³ an hypothetic schema which has been widely accepted. Finding that the large cells in the anterior horn of the spinal cord gave off processes of different kinds, one branched, the other unbranched, he held that the latter process was the origin of the axis267 cylinder of a nerve-fibre, whereas the branched process was protoplasm which divided and subdivided¹¹⁴, and formed the connection between one cell and another. Gerlach has modified this by supposing that the minute fibrils of the branching process reunite and form an axis cylinder (Fig. 18). There is no doubt that some processes terminate in a fine network; and there is a probability (not more) that the unbranched process is always continuous with the axis cylinder of a motor nerve, as we know it sometimes is with that of a dark-bordered fibre in the white substances. This, though probable, is, however, very far from having been demonstrated. Once or twice K?lliker, Max Schultze, and Gerlach have followed this unbranched process as far as the root of a motor nerve; and they infer that although it could not be traced further, yet it did really join an axis cylinder there. In support Of this inference came the observations of Koschennikoff,148 that in the cerebrum and cerebellum, processes were twice seen continuous with dark-bordered nerve-fibres. But the extreme rarity of such observations amid thousands of cells is itself a ground for hesitation¹¹⁵ in accepting a generalized interpretation, the more so since we have Henle’s observation of the similar entrance of a branched process into the root.149 Now it must be remembered that the branched process is by no anatomist at present regarded as the origin of the axis cylinder; so that if it can enter the root without being the origin of a nerve-fibre, we are not entitled to assume that the entrance of the unbranched process has any other significance (on this head compare § 145), especially when we reflect that no trustworthy observer now professes¹¹⁷ to have followed a nerve-fibre of the posterior root right into a multipolar cell. Figures,268 indeed, have been published which show this, and much else; but such figures are diagrams, not copies of what is seen. They belong to Imaginary Anatomy.150 The relation of the cell-process to the nerve-fibre will be discussed anon.

 

Fig. 19.—Anastomosing nerve-cells (after Gratiolet). a, body of the cell; c, process of uniting two cells; d, branching process.

125. A word in passing on the contradictory¹¹⁸ assertions respecting the anastomosis of nerve-cells. That the gray substance forms a continuum of some kind is certain from the continuity of propagation of a stimulus¹¹⁹. But it is by no means certain that one cell is directly united to its neighbor by a cell-process. Eminent¹²⁰ authorities assert that such direct union never takes place; others, that it is a rare and insignificant¹²¹ fact; others, that it is constant, and “demanded by physiological postulates.” I will not,269 in the presence of distinct affirmations, venture to deny that such appearances as are presented in Fig. 19 may occasionally be observed; the more so as I have myself seen perhaps half a dozen somewhat similar cases; but it is the opinion of Deiters and K?lliker that all such appearances are illusory.151 Granting that such connections occur, we cannot grant this to be the normal mode; especially now the more probable supposition is that the connection is normally established by means of the delicate ramifications¹²² of the branching processes.

Imaginary Anatomy has not been content with the cells of the anterior horn being thus united together, to admit of united action, but has gone further, and supposed that the cells of the posterior horn, besides being thus united, send off processes which unite them with the cells of the anterior horn—and thus a pathway is formed for the transmission of a sensory impression, and its conversion¹²³ into a motor impulse. What will the reader say when informed that not only has no eye ever beheld¹²⁴ such a pathway, but that the first step—the direct union of the sensory nerve-fibre with a cell in the posterior horn—is confessedly not visible?

126. The foregoing criticisms will perhaps disturb the reader who has been accustomed to theorize on the data given in text-books; but he may henceforward be more cautious in accepting such data as premises¹²⁵ for deduction, and will look with suspicion on the many theories which have arisen on so unstable¹²⁶ a basis. When we reflect how completely the modern views of the nervous system, and the physiological, pathological, and psychological explanations based on these views, are dominated by the current270 notions of the nerve-cell, it is of the last importance that we should fairly face the fact that at present our knowledge even of the structure of the nerve-cell is extremely imperfect; and our knowledge of the part it plays—its anatomical relations and its functional¹²⁷ relations—is little more than guesswork!

THE NERVES.

 

127. We now pass to the second order of organites; and here our exposition will be less troubled by hesitations¹²⁸, for although there is still much to be learned about the structure and connections of the nerve-fibres, there is also a solid foundation of accurate knowledge.

 

Fig. 20.—a, axis cylinder formed by the fibrils of the cell contents, and at a’ assuming the medullary sheath; b, naked axis cylinder from spinal cord.

A nerve is a bundle of fibres within a membranous¹²⁹ envelope supplied with blood-vessels. Each fibre has also its separate sheath, having annular¹³⁰ constrictions at various intervals¹³². It is more correctly named by many French anatomists a nerve-tube rather than a nerve-fibre; but if we continue to use the term fibre, we must reserve it for those organites which have a membranous sheath, and thereby¹³³ distinguish it from the more delicate fibril which has none.

The nerve tube or fibre is thus constituted: within the sheath lies a central band of neuroplasm identical with the neuroplasm of nerve-cells, and known as the axis cylinder; surrounding this band is an envelope of whitish substance, variously styled myeline, medullary sheath, and white substance of Schwann: it is closely similar to the chief constituent of the yolk¹³⁴ of egg, and to its presence is due the whitish color of the fibres, which in its absence are grayish. The axis cylinder must be understood as the primary and essential element, because not only are there nerve-fibrils destitute¹³⁵ both of sheath and myeline yet fulfilling the office of Neurility, but at their terminations,271 both in centres and in muscles, the nerve-fibres always lose sheath and myeline, to preserve only the neuroplasmic threads of which the axis cylinder is said to be composed. In the lowest fishes, in the invertebrates¹³⁶, and in the so-called sympathetic fibres of vertebrates, there is either no myeline, or it is not separated from the neuroplasm.

128. Nerve-fibres are of two kinds—1°. The dark-bordered or medullary fibres, which have both sheath and myeline, as in the peripheral¹³⁷ system; or only myeline, without the sheath, as in the central system. 2°. The non-medullary fibres, which have the sheath, without appreciable¹³⁸ myeline—such are the fibres of the olfactory¹³⁹, and the pale fibres of the sympathetic.

Nerve-fibrils are neuroplasmic threads of extreme delicacy, visible only under high magnifying powers (700–800), which abound in the centres, where they form networks. The fibrils also form the terminations of the fibres. Many fibrils are supposed to be condensed in one axis cylinder. This is represented by Max Schultze in Figs¹⁴⁰. 17 and 20.

129. As may readily be imagined, the semi-liquid nature of the272 neuroplasm throws almost insuperable difficulties in the way of accurately¹⁴¹ determining whether the axis cylinder in the living nerve is fibrillated or not; whether, indeed, any of the aspects it presents in our preparations are normal. Authorities are not even agreed as to whether it is a pre-existent solid band of homogeneous substance, or a bundle of primitive¹⁴² fibrils, or a product of coagulation.152 Rudanowsky’s observations on frozen nerves convinced him that the cylinder is a tubule with liquid contents.153 My own investigations¹⁴³ of the nerves of insects and molluscs incline me to the view of Dr. Schmidt of New Orleans, namely, that the cylinder axis consists of minute granules arranged in rows and united by a homogeneous interfibrillar substance, thus forming a bundle of granular fibrils enclosed in a delicate sheath154—in other words, a streak¹⁴⁴ of neuroplasm which has a fibrillar disposition¹⁴⁵ of its granules. We ought to expect great varieties in such streaks¹⁴⁶ of neuroplasm; and it is quite conceivable that in the Rays and the Torpedo¹⁴⁷ there are axis cylinders¹⁴⁸ which are single fibrils, and others which are bundles, with finely granulated interfibrillar substance.155

The fibres often present a varicose aspect, as represented in Fig. 21. It is, however, so rarely observed in the fresh tissue, that many writers regard it (as well as the double contour) as the product of preparation.156 It is, indeed, always visible after the application of water.

273 We need say no more at present respecting the structure of nerve-fibres, except to point out that we have here an organite not less complex than the cell.

 

Fig. 21.—Nerve-fibres from the white substance of the cerebrum. a, a, a, the medullar contents pressed out of the tube as irregular drops.

THE NEUROGLIA.

 

130. Besides cells and fibres, there is the amorphous substance, which constitutes a great part of the central tissue, and also enters largely into the peripheral tissue. It consists of finely granular substance, and a network of excessively delicate fibrils, with nuclei interspersed. Its character is at present sub judice. Some writers hold it to be nervous, the majority hold it to be simply one of the many forms of connective tissue: hence its name neuroglia, or nerve-cement.

274 In the convolutions of the frozen brain Walther finds the cells and fibres imbedded in a structureless semi-fluid substance wholly free from granules; the granules only appear there when cells have been crushed. It is to this substance he attributes the fluctuation¹⁴⁹ of the living brain under the touch, like that of a mature abscess; the solidity which is felt after death is due to the coagulation of this substance. Unhappily we have no means of determining whether the network visible under other modes of investigation is present, although invisible, in this substance. The neuroglia, as it appears in hardened tissues, must therefore be described with this doubt in our minds.

If we examine a bit of central gray substance where the cells and fibres are sparse¹⁵⁰, we see, under a low power, a network of fibrils in the meshes¹⁵¹ of which lie nerve-cells. Under very high powers we see outside these cells another network of excessively fine fibrils embedded in a granular ground substance, having somewhat the aspect of hoar-frost, according to Boll. It is supposed that the first network is formed by the ultimate ramifications of the nerve-cell processes, and that the second is formed by ramifications of the processes of connective cells. In this granular, gelatinous, fibrillar substance nuclei appear, together with small multipolar cells not distinguishable from nerve-cells except in being so much smaller. These nuclei are more abundant in the tissue of young animals, and more abundant in the cerebellum than in the cerebrum. The granular aspect predominates the fresher the specimen¹⁵², though there is always a network of fibrils; so that some regard the granules as the result of a resolution of the fibrils, others regard the fibrils as the linear crystallization (so to speak) of the granules.157

275 131. Such is the aspect of the neuroglia. I dare not venture to formulate¹⁵³ an opinion on the histological question whether this amorphous substance is neural, or partly neural and partly connective (a substance which is potentially both, according to Deiters and Henle), or wholly connective. The question is not at present to be answered decisively, because what is known as connective tissue has also the three forms of multipolar cells, fibrils, and amorphous substance; nor is there any decisive mark by which these elements in the one can be distinguished¹⁵⁴ from elements in the other. The physical and chemical composition of Neuroglia and Neuroplasm are as closely allied¹⁵⁵ as their morphological structure. And although in the later stages of development the two tissues are markedly distinguishable, in the early stages every effort has failed to furnish a decisive indication.158 Connective tissue is dissolved by solutions which leave nerve-tissue intact. Can we employ this as a decisive test? No, for if we soak a section of the spinal cord in one of these solutions, the pia mater and the membranous septa which ramify from it between the cells and fibres disappear, leaving all the rest unaltered. This proves that Neuroglia is at any rate chemically different from ordinary connective tissue, and more allied to the nervous. As to the staining process, so much relied on, nothing requires greater caution in its employment. Stieda found that the same parts were sometimes stained and sometimes not; and Mauthner observed that in some cells both contents and nucleolus were stained, while the nucleus remained clear,276 in other cells the contents remained clear; and some of the axis cylinders were stained, the others not.159 Lister found that the connective tissue between the fibres of the sciatic nerve, as well as the pia mater, were stained like the axis cylinders;160 and in one of my notes there is the record of both (supposed) connective cells and nerve-cells being stained alike, while the nerve-fibres and the (supposed) connective fibres were unstained. Whence I conclude that the supposition as to the nature of the one group being different from that of the other was untenable, if the staining test is to be held decisive.

132. The histological question is raised into undue¹⁵⁶ importance because it is supposed to carry with it physiological consequences which would deprive the neuroglia of active co-operation in neural processes, reducing it to the insignificant position of a mechanical support. I cannot but regard this as due to the mistaken tendency of analytical interpretation, which somewhat arbitrarily fastens on one element in a complex of elements, and assigns that one as the sole agent. Whether we call the neuroglia connective or neural, it plays an essential part in all neural processes, probably a more important part than even the nerve-cells, which usurp¹¹ exclusive attention! To overlook it, or to assign it a merely mechanical office, seems to me as unphysiological as to overlook blood-serum, and recognize the corpuscles as the only nutrient¹⁵⁷ elements. The notion of the neuroglia being a mere⁶⁹ vehicle of support for the blood-vessels arises from not distinguishing between the alimental and instrumental offices. In the function of a limb, bone is a co-operant. In the function of a centre, connective tissue is a co-operant; so that even if we acknowledge neuroglia277 to be a special form of connective tissue, it is an agent in neural processes; what its agency is, will be hereafter considered.

Following Bidder¹⁵⁸ and Kupffer, the Dorpat school proclaimed the whole of the gray substance of the posterior half of the spinal cord to be connective tissue; and Blessig maintained that the whole of the retina, except the optic fibres, was connective tissue.161 Even those anatomists who regarded this as exaggerated, admitted that connective tissue largely enters into the gray substance, especially if the granular ground substance be reckoned as connective, the nerve-cells being very sparse in the posterior region. Be it so. Let us admit that the gray matter of the frog’s spinal cord is mainly composed of neuroglia, in which a very few multipolar nerve-cells are embedded. What must our conclusion be? Why, that since this spinal cord is proved to be a centre of energetic and manifold reflex actions—even to the extent of forcing many investigators¹⁵⁹ to attribute sensation and volition¹⁶⁰ to it—this is proof that connective tissue does the work of nerve-tissue, and that the neuroglia is more important than nerve-cells!

Three hypotheses are maintainable—1°. The neuroglia is the amorphous ground-substance of undeveloped tissue (neuroplasm) out of which the cells and fibres of nerve-tissue and connective tissue are evolved. 2°. It is the product of dissolved nerve cells and fibres. 3°. It is the undeveloped stage of connective tissue. For physiological purposes we may adopt any one of these views, provided we keep firm hold of the fact that the neuroglia is an essential element, and in the centres a dominant¹⁶¹ element. To make this clear, however, we must inquire more closely into the relations of the three elements, nerve-cells, fibres, and neuroglia.

278

THE RELATIONS OF THE ORGANITES.

 

133. In enumerating¹⁶² among the obstacles to research the tendency to substitute hypothetic deductions¹⁶³ in place of objective facts, I had specially¹¹⁶ in my mind the wide-reaching influence of the reigning¹⁶⁴ theories of the nerve-cell. Had we a solidly established theory of the cell, equivalent, say, to our theory of gas-pressure, we should still need caution in allowing it to override exact observation; but insecure as our data are, and hypothetical as are the inferences respecting the part played by the cell, the reliance placed on deductions from such premises is nothing less than superstition. Science will take a new start when the whole question is reinvestigated on a preliminary setting aside of all that has been precipitately¹⁶⁵ accepted respecting the office of the cell. This exercise of the imagination, even should the reigning theories subsequently be confirmed, would not fail to bring many neglected facts into their rightful place.

I am old enough to remember when the cell held a very subordinate position in Neurology, and now my meditations¹⁶⁶ have led me to return, if not to the old views of the cell, at least to something like the old estimate of its relative importance. Its existence was first brought prominently forward by Ehrenberg in 1834, who described its presence in the sympathetic ganglia; and by Remak in 1837, who described it in the spinal ganglia. For some time afterwards the ganglia and centres were said to contain irregular masses of vesicular matter which were looked on as investing the fibres; what their office was, did not appear. But there rapidly arose the belief that the cells were minute batteries in which “nerve-force” was developed, the fibres serving merely as conductors. Once started on this track, Hypothesis had free279 way, and a sort of fetichistic deification of the cell invested it with miraculous¹⁶⁷ powers. In many works of repute we meet with statements which may fitly take their place beside the equally grave statements made by savages¹⁶⁸ respecting the hidden virtues¹⁷⁰ of sticks and stones. We find the nerve-cells credited with “metabolic¹⁷¹ powers,” which enable them to “spiritualize impressions, and materialize ideas,” to transform sensations into movements, and elaborate sensations into thoughts; not only have they this “remarkable¹⁷² aptitude¹⁷³ of metabolic local action,” they can also “act at a distance.”162 The savage¹⁶⁹ believes that one pebble¹⁷⁴ will cure diseases, and another render him victorious¹⁷⁵ in war; and there are physiologists who believe that one nerve-cell has sensibility, another motricity, a third instinct, a fourth emotion, a fifth reflexion: they do not say this in so many words, but they assign to cells which differ only in size and shape, specific qualities. They describe sensational¹⁷⁶, emotional, ideational, sympathetic, reflex, and motor-cells; nay, Schr?der van der Kolk goes so far as to specify¹⁷⁷ hunger-cells and thirst-cells.163280 With what grace can these writers laugh at Scholasticism?

134. The hypothesis of the nerve-cell as the fountain of nerve-force is supported by the gratuitous¹⁷⁸ hypothesis of cell-substance having greater chemical tension and molecular¹⁸⁰ instability than nerve-fibre. No evidence has been furnished for this; indeed the only experimental evidence bearing on this point, if it has any force, seems directly adverse¹⁸¹ to the hypothesis. I allude¹⁸² to the experiments of Wundt, which show that the faint stimulus capable of moving a muscle when applied directly to its nerve, must be increased if the excitation has to pass through the cells by stimulation¹⁸³ of the sensory nerve.164 Wundt interprets this as proving that the cells retard¹⁸⁴ every impulse, whereby they are enabled to store up latent force. The cells have thus the office of locks in a canal, which cause the shallow stream to deepen at particular places. I do not regard this interpretation as satisfactory; but the fact at any rate seems to prove that so far from the cells manifesting greater instability than the fibres, they manifest less.

135. The hypothesis of nerve-force being developed in the ganglia, gradually assumed a more precise expression when the nerve-cells were regarded as the only important elements of a ganglion. It has become the foundation-stone of Neurology, therefore very particular care should be taken to make sure that this foundation rests on clear and indisputable evidence. Instead of that, there is absolutely no evidence on which it can rest; and there is much evidence decidedly opposed to it. Neither structure281 nor experiment points out the cells as the chief agents in neural processes. Let us consider these.

Fig. 22 shows the contents of a molluscan ganglion which has been teased out with needles.

 

Fig. 22.—Cells, fibres, and amorphous substance from the ganglion of a mollusc

(after Bucholtz).

282 The cells are seen to vary in size, but in all there is a rim⁶⁴ of neuroplasm surrounding the large nucleus, and from this neuroplasm the fibre is seen to be a prolongation. The dotted substance in the centre is the neuroglia. Except in the possession of a nucleus, there is obviously here no essential difference in the structure of cell and fibre.

 

Fig. 23—Fibres from the auditory nerve. a, the axis cylinder; b, the cellular¹⁸⁵ enlargement; c, the medullary sheath.

Now compare this with Fig. 23, representing three fibres from the auditory nerve.

Here the cell substance, as Max Schultze remarks, “is a continuation of the axis cylinder, and encloses the nucleus. The medulla commonly ceases at the point where the axis enters the cell, to reappear at its exit; but it sometimes stretches across the cell to enclose it also: so that such a ganglion cell is in truth simply the nucleated portion of the cylinder axis.”165 There are many places in which fibres are thus found with cells inserted in their course as swellings: in the spinal ganglia of fishes these are called bipolar cells; they are sometimes met with even in the cerebellum; but oftener in peripheral nerves, where they are mostly small masses of granular neuroplasm from which usually a branching of the fibre takes place. The point to which attention is called283 is that in some cases, if not in all, the nerve-fibre is structurally¹⁸⁶ continuous with the cell contents. The two organites—fibre and cell—differ only as regards the nucleus and pigment. Haeckel, who affirms that in the crayfish (Astacus fluviatilis) he never saw a cell which did not continue as a fibre, thinks there is always a marked separation of the granular substance from its “hyaline protoplasm,” and that only this latter forms the axis cylinder. But although my observations agree with this as a general fact, I have seen even in crayfish the granular substance prolonged into the axis cylinder; and in other animals the granular substance is frequently discernible.

Indeed it may be said that anatomists are now tolerably unanimous as to the axis cylinder being identical with the protoplasmic cell substance. If this be so, we have only to recall the principle of identity of property accompanying identity of structure, to conclude that whatever properties we assign to the cells (unless we restrict these to the nucleus and pigment) we must assign to the axis cylinders. We can therefore no longer entertain the hypothesis of the cells being the fountains or reservoirs of Neurility; the less so when we reflect that cells do not form the hundredth part of nerve-tissue: for even the gray substance bears but a small proportion to the white; and of the gray substance, Henle estimates that one half is fibrous, the rest is partly cellular, partly amorphous. Those who derive¹⁸⁷ Neurility from the cells, forget that although the organism begins as a cell, and for some weeks consists mainly of cells, yet from this time onwards there is an ever-increasing preponderance of cell-derivatives—fibres, tubes, and amorphous substance—and corresponding284 with this is the ever-increasing power and complexity¹⁸⁸ of the organism.

136. From another point of view we must reject the hypothesis. Not only does the evidence which points to the essential continuity in structure of nerve cell and fibre discredit¹⁸⁹ the notion of their physiological diversity, but it is further supported by the fact that although the whole nervous system is structurally continuous, an immense mass of nerve-fibres have no immediate¹⁹⁰ connection with ganglionic cells:—neither springing from nor terminating in such cells, their activity cannot be assigned to them. To many readers this statement will be startling. They have been so accustomed to hear that every fibre begins or terminates in a cell, that a doubt thrown on it will sound paradoxical. But there is an equivoque here which must be got rid of. When it is said that every fibre has its “origin” in a cell, this may be true if origin mean its point of departure in evolution, for “cells” are the early forms of all organites; but although every organite is at first a cell, and in this sense a nerve-fibre must be said to originate in a cell, we must guard against the equivoque which arises from calling the highly differentiated¹⁹¹ organite, usually designated ganglionic cell, by the same name as its starting-point. On this ground I suggest the term neuroblast, in lieu of nerve-cell, for the earlier stages in the evolution of cell and fibre. Both Embryology and Anatomy seem to show that cell and fibre are organites differentiated from identical neuroblasts, with a somewhat varying history, so that in their final stages the cell and fibre have conspicuous differences in form with an underlying¹⁹² identity; just as a male and female organism starting from identical ova, and having essential characters in common, are yet in other characters conspicuously¹⁹³ unlike. The multipolar cell is not necessarily the origin of a nerve-fibre,285 although it is probable that some short fibres have their origin in the prolongations of cells. Although the latter point has not, I think, been satisfactorily established, except in the invertebrata, I see no reason whatever to doubt its probability; what seems the least reconcilable with the evidence is the notion that all fibres arise as prolongations from ganglionic cells, instead of arising independently as differentiations from neuroblasts. The reader will observe that my objection to the current view is purely¹⁹⁵ anatomical; for the current view would suit my physiological interpretations equally well, and would be equally irreconcilable¹⁹⁶ with the hypothesis of the cell as the source of Neurility, so long as the identity of structure in the axis cylinder and cell contents is undisputed.

137. The evidence at present stands thus: There are numerous multipolar cells which have no traceable connection with nerve-fibres; and fibres which have no direct connection with multipolar cells. By the first I do not mean the disputed apolar cells, I mean cells in the gray substance of the centres which send off processes that subdivide and terminate as fibrils in the network of the Neuroglia (Figs. 16, 18). It is indeed generally assumed that these have each one process—the axis-cylinder process—which is prolonged as a nerve-fibre; nor would it be prudent¹⁹⁷ to assert that such is never the case; though it would be difficult to distinguish between a fibre which had united with a process and a fibre which was a prolongation of a process, in both cases the neuroplasm being identical. I only urge that the assumption is grounded not on anatomical evidence, but on a supposed necessary postulate. All that can be demonstrated is that some processes terminate in excessively fine fibrils; and occasionally in thousands of specimens¹⁹⁸ processes have been traced into dark-bordered fibres. It is true that they often present appearances which286 have led to the inference that they did so terminate—appearances so deceptive¹⁹⁹ that Golgi and Arndt independently record observations of unbranched processes having the aspect of axis cylinders being prolonged to a considerable distance (600 μ in one case), yet these were found to terminate not in a dark-bordered fibre, but in a network of fibrils.166

138. While it is thus doubtful whether dark-bordered fibres are always immediately connected with cells, it is demonstrable that multitudes of fibres have only an indirect connection with cells, being developed as outgrowths from other fibres. Dr. Beale considers that in each such outgrowths have their origin in small neuroplasmic masses (his “germinal matter”). That is another question. The fact here to be insisted on is that we often find groups of cells with only two or three fibres, and groups of fibres where very few cells exist. Schr?der van der Kolk says that in a sturgeon (Accipenser sturio) weighing 120 pounds he found the spinal cord scarcely thicker than that of a frog; the muscles of this fish are enormous, and its motor nerves abundant; yet these nerves entered the cord by roots no thicker than a pig’s bristle²⁰⁰; and in the very little gray matter of the cord there was only a cell here and there found after long search. Are we to suppose that these rare cells were the origins of all the motor and sensory nerves? A similar want of correspondence may be noticed elsewhere. Thus in the spinal cord of the Lamprey my preparations show287 very few cells in any of the sections, and numerous sections show none at all. Stieda counted only eight to ten cells in each horn of some osseous fishes, except at the places where the spinal roots emerged. In the eel²⁰¹ and cod²⁰² he found parts of the cord quite free from cells, and in other parts found two, three, never more than ten. In birds he counted from twenty-five to thirty. Particular attention is called to this fact of the eel’s cord being thus deficient²⁰³, because every one knows the energetic reflex action of that cord, each separate segment of which responds to peripheral stimulation.

It may indeed be urged that these few cells were the origin of all the fibres, the latter having multiplied by the well-known process of subdivision; and in support of this view the fact may be cited of the colossal²⁰⁴ fibres of the electric fishes, each of which divides into five-and-twenty fibres, and in the electric eel each fibre is said by Max Schultze to divide into a million of fibrils. But I interpret this fact otherwise. It seems to me to prove nothing more than that the neuroplasm has differentiated into few cells and many fibres. And my opinion is grounded on the evidence of Development, presently to be adduced. If we find (and this we do find) fibres making their appearance anywhere before multipolar cells appear, the question is settled.

139. Dr. Beale regards the large caudate cells of the centres as different organites from the oval and pyriform cells, and thinks they are probably stations through which fibres having different origins merely pass, and change their directions; and Max Schultze says that no single fibril has been found to have a central origin; every fibril arises at the periphery, and passes through a cell, which is thus crossed by different fibrils.167 (Comp. Fig. 17.)

288 The teaching of Development is on this point of supreme²⁰⁵ importance. Unhappily there has not yet been a sufficient collection of systematic²⁰⁶ observations to enable us to speak very confidently as to the successive stages, but some negative evidence there is. The changes take place with great rapidity, and the earliest stages have hardly been observed at all. Although for several successive years I watched the development of tadpoles²⁰⁷, the difficulties were so great, and the appearances so perplexing, that the only benefit I derived²⁰⁸ was that of being able the better to understand the more successful investigations of others. Four or five days after fecundation is the earliest period of which I have any recorded observation; at this period the cerebral²⁰⁹ substance appeared as a finely granular matter, having numerous lines of segmentation marking it off into somewhat spherical²¹⁰ and oval masses, interspersed with large granules and fat globules. Here and there hyaline substance appeared between the segments. Similar observations have since been recorded by Charles Robin in the earliest stages of the Triton.168 He says that when the external gills presented their first indications, nuclei appeared, each surrounded by a rim of hyaline substance, from which a pale filament²¹¹ was prolonged at one end, sometimes one at both ends, and this filament subdivided as it grew in length until it had all the appearance of an axis cylinder. This, however, he says, is a striation, not a fibrillation; he refuses to admit that the axis cylinder is a bundle of fibrils. He further notices the simultaneous appearance of amorphous substance;289 and as this is several days before there is any trace of a pia mater, or proper connective tissue, he urges this among the many considerations which should prevent the identification of neuroglia with connective tissue.

In a very young embryo of a mole¹⁷⁹ (I could not determine its age) the cortex of the hemispheres showed granular amorphous substance, in which were embedded spherical masses of somewhat paler color, which had no nuclei, and were therefore not cells. Besides these, there were nucleated masses (apolar cells, therefore) and more developed cells, unipolar, bipolar, and tripolar. Not a trace of a nerve-fibre was visible. In agreement with this are the observations of Masius and Van Lair²¹², who cut out a portion of the spinal cord in a frog, and observed the regenerated²¹³ tissue after the lapse²¹⁴ of a month. It contained apolar, bipolar, and multipolar cells, together with “corpuscles without processes, for the most part larger than the cells, and appearing to be mere agglomerations²¹⁵ of granules,”—these latter I suppose to have been what I describe as segmentations of the undeveloped substance. Gray fibres, with a few varicose fibres, also appeared.169

140. The admirable investigations of Franz Boll have given these observations a new significance. He finds in the cerebral substance of the chick on the third or fourth day of incubation a well-marked separation between the neuroglia and nerve-tissue proper. Fig. 24, A, represents three nerve-cells, each with its nucleus and nucleolus, and each surrounded with its layer of neuroplasm. The other four masses he regards as nuclei of connective tissue. Three days later the distinction between the two is more marked (Fig. 24, B). Not only have the nerve-cells acquired an increase of neuroplasm, they also present indications of their future processes, which at the twelfth day290 are varicose (Fig. 24, C). (All this while the connective corpuscles remain unchanged.) Although Boll was unable to trace one of these processes into nerve-fibres, he has little doubt that they do ultimately become (unite with?) axis cylinders.

 

Fig. 24.—Embryonic nerve-cells.

 

Fig. 25.—Embryonic nerve-fibres.

It is difficult to reconcile such observations with the hypothesis of the cells being simply points of reunion of fibrils. We see here multipolar cells before any fibrils appear. Respecting the development of the white substance, i. e. the nerve-fibres, Boll remarks that in the corpus callosum of the chick the first differentiation¹⁹⁴ resembles that of the gray substance.

The polygonal²¹⁶ and spindle-shaped cells represented in Fig. 25, A, are respectively starting-points of connective and neural tissues. The spindle-shaped cells elongate²¹⁷, and rapidly become bipolar. This is supposed to result in the whole cell becoming transformed into a fibre, the nucleus and nucleolus vanishing; but the transformation²¹⁸ is so rapid that he confesses that he was unable to trace its stages; all that can positively be asserted is that one or two days after the appearance presented in Fig. 25, B, the aspect changes to that of fibrils. The columns of polygonal cells between which run these fibrils, he regards as the connective corpuscles described by several anatomists in the white substance both of brain and cord, and which are sometimes declared to be multipolar nerve-cells.170

141. Dr. Schmidt’s observations on the human embryo were of course on tissue at a very much later stage.291 According to him, the fibrils of the axis cylinders are formed by the linear disposition and consolidation²¹⁹ of elementary granules. The fibrils thus formed are separated by interfibrillar granules which in time become fibrils. Not earlier than three months and a half does the formation of individual axis cylinders begin by the aggregation292 of these fibrils into minute bundles, which are subsequently surrounded by a delicate sheath.171

142. With respect to the transition of the spindle-shaped cells into fibrils, since there is a gap in the observations of Boll, and since those of Schmidt are subsequent to the disappearance²²⁰ of the cells, and in both cases all trace of nucleus has disappeared, I suggest that we have here an analogy with what Weismann has recorded of the metamorphoses of insects. In the very remarkable memoir²²¹ of that investigator172 it is shown that the metamorphoses do not take place by a gradual modification²²² of the existing organs and tissues, but by a resolution of these into their elements, and a reconstruction of their elements into tissues and organs. The muscles, nerves, trache?, and alimentary²²³ canal, undergo what may be called a fatty degeneration, and pass thence into a mere blastema. It is out of these ruins of the old tissues that the new tissues are reconstructed. On the fourth day the body of the pupa is filled with a fluid mass—a plasma²²⁴ composed of blood and dissolved tissues. The subsequent development is thus in all essential respects a repetition of that which originally took place in the ovum.173

293 Two points are especially noticeable: First, that in this resolved mass of granules and fat globules there quickly appear large globular masses which develop a fine membrane²²⁵, and subsequently nuclei. A glance at the figure 51 of Weismann’s plates reveals the close resemblance to the earliest stages of nerve-cells; and the whole process recalls the regeneration of nerves and nerve-centres after their fatty degeneration.

Secondly, the nerves reappear in their proper places in the new muscles, and this at a time when the nerve-centres are still unformed; so that the whole peripheral system is completely rebuilt in absolute independence of the central system. The idea, therefore, that nerve-fibres are the products of ganglia must be relinquished²²⁶. This idea is further discountenanced by Boll’s observations, which show that the fibre-cells are from the first different from the ganglionic cells; and by the observations of Foster and Balfour, that “fibres are present in the white substance on the third day of incubation”; whereas cell processes do not appear until the eighth day. Foster and Balfour are inclined to believe “that even on the seventh day it is not possible to trace any connection between the cells and fibres.” In the later stages, the connection is perhaps established.174

294 143. We may, I think, conclude from all this that in the higher vertebrates the white substance of brain and cord is not the direct product of the gray substance; in other words, that here nerve-fibres, even if subsequently in connection with the ganglionic cells, have an independent origin. They may grow towards and blend with cell processes; they are not prolongations of those processes. They may be identical in structure and property, as one muscle is identical with another, but one is not the parent of the other.

144. Sigmund Mayer emphatically declares that in no instance has he traced a cell process developed into a dark-bordered nerve-fibre. The process, he says, may often be traced for a certain distance alongside of a fibre; but it then suddenly ceases, whereas the fibre is seen continuing its course unaltered. Still more conclusive²²⁷ is the evidence afforded by nerves having only very few fibres (2–4 sometimes in the frog), which have, nevertheless, a liberal supply of cells, visible without preparation. Valentin counted twenty-four cells in a nerve which had but two fibres.175 Now although it is possible to295 explain the presence of numerous fibres with rare cells either as due to subdivisions of fibres, or to the fibres having cells elsewhere for their origin, it is not thus that we can explain the presence of numerous cells which have no fibres developed from their processes.

145. With regard to this observation of the cell process running alongside of the fibre, the recent researches of Ranvier may throw some light on it. He describes the cells in the spinal ganglia as all unipolar; each single process pursues a more or less winding²²⁸ course as a fibril, often blending with others, till it reaches one of the fibres from the sensory root. It blends with this fibre at the annular constriction¹³¹ of the fibre, becoming here incorporated with it, so that a T-shaped fibre is the result.176 If this should be confirmed, it would reconcile many observations; but it would greatly disturb all current interpretations. Ranvier remarks that it is no longer tenable to suppose that the ganglionic cell is a centre, sensory or motor, receiving the excitation or sending forth²²⁹ a motor impulse; for if the fibril issuing from a cell becomes laterally²³⁰ soldered²³¹ to a nerve-fibre, there is no possibility of saying in which direction this cell receives the excitation, nor in which it transmits the impulse.

296 146. We have seen good reason to conclude that the essential element of the nerve—the axis cylinder—is the same substance as the neuroplasm which forms the essential element of the cell. At any rate, we are quite certain that the cell process is neuroplasm. On this ground there is no difficulty in understanding that a cell process may sometimes be drawn⁹⁰ out into an axis cylinder (as indeed we see to be the case in the invertebrata and electric fishes); while again in numerous other cases the nerve-fibre has an independent origin, being, in short, a differentiation from the neuroplasm which has become a fibre instead of a cell. It is clear from the observations of Rouget on Development, and of Sigmund Mayer on Regeneration, that fibres, nuclei, and cells become differentiated from the same neuroplasm, those portions which are not converted into fibres remaining first as lumps of neuroplasm, then acquiring a nucleus, and some of these passing into cells. I mean that between fibres, nuclei, and cells there are only morphological differences in an identical neuroplasm.177 If this is in any degree true, it will not only explain how fresh fibres may be developed in the course of fibres, branching from them as from trunks, and branchlets from branchlets, twigs²³² from branchlets, the same conditions of growth being present throughout; it will also completely modify the notion of any physiological distinction between cell and fibre greater than can be assigned to the morphological differences. We shall then no longer suppose that the cell is the fountain whence the fibre draws its nutrition and its “force”; and this will be equally the case even if we admit that a cell is, so to speak, the germ from which a whole plexus of fibres was evolved, for no one will pretend that the “force” of an organism is directly derived297 from the ovum, or that the ovum nourishes the organism.

147. At this stage of the discussion it is needful to consider a point which will spontaneously occur to every instructed reader, I mean the interesting fact discovered by Dr. Waller, that when a sensory root was divided, the portion which was still in connection with the ganglion remained unaltered, whereas the portion which was only in connection with the spinal cord degenerated²³⁴; and vice³⁷ versa, when a motor root was divided, the portion connected with the cord remained unaltered, the portion severed²³⁵ from the cord degenerated. The observation has been frequently confirmed, and the conclusion drawn has been that the cells in the ganglion of the posterior root are the nutritive centres of posterior nerves, the cells in the anterior horn of the cord being the nutritive centres of the anterior nerves. Another interpretation is however needed, the more so because the fact is not constant.178 True of some nerves, it is not true of others. Vulpian found that when he cut out a portion of the lingual²³⁶ nerve, and transplanted it by grafting²³⁷ under the skin of the groin, where of course it was entirely²³⁸ removed from all ganglionic influence, it degenerated, but it also regenerated. Pathological observations convinced Meissner that the ganglia are wholly destitute of an influence on the nutrition of the vagus; and Schiff proved experimentally298 that other ganglia were equally inoperative, since motor nerves could be separated from the spinal cord without degeneration.179 Not however to insist on this, nor on the other facts of regeneration, in the absence of ganglionic influence, let us remark that Dr. Waller’s examples would not be conclusive unless the teaching of Embryology could be disproved. That nerves degenerate²³³ when separated from ganglia is a fact; but it is also a fact that muscles degenerate when separated from a nerve-centre; yet we do not suppose the nerve-centre to nourish the muscles. And against the fact that the sensory nerve remains²³⁹ unaltered only in that portion which is connected with the ganglion, we must oppose the observations of K?lliker and Schwalbe,180 who affirm that none of the fibres which enter the posterior columns of the spinal cord have any direct connection with the cells of the ganglion on the posterior root. The cells of this ganglion they declare to be unipolar (in the higher vertebrates), and the fibres in connection with these cells are not those which pass to the cord, but all of them pass to the periphery. According to Ranvier, the fibres from the cells join the fibres of the posterior root. Schwalbe found that if the spinal nerve be firmly grasped and steadily²⁴⁰ drawn, it will often be pulled from its sheath, and the ganglion laid bare;181 in this ganglion all the cells are found undisturbed, which could not be the case had fibres from those cells entered the cord, since the traction²⁴¹ would necessarily have disturbed them.

299

RECAPITULATION.

 

148. At the opening of this chapter mention was made of the besetting²⁴² sin of the analytical tendency, namely, to disregard the elements which provisionally had been set aside, and not restore them in the reconstruction of a synthetical²⁴³ explanation. Familiar experiences tell us that a stimulus applied to the skin is followed by a muscular movement, or a glandular²⁴⁴ secretion²⁴⁵; sometimes this takes place without any conscious sensation; sometimes we are distinctly conscious of the stimulus; and sometimes we consciously will the movement. These facts the physiologist¹³ tries to unravel²⁴⁶, and to trace the complicated processes involved. The neurologist of course confines himself exclusively to the neural processes; all the other processes are provisionally left out of account. But not only so: the analytical tendency is carried further, and even in the neural process the organs are neglected for the sake of the nervous tissue, and the nervous tissue for the sake of the nerve-cell. The consequence has been that we have an explanation offered us which runs thus:—

149. The nerve-cell is the supreme element, the origin of the nerve-fibre, and the fountain of nerve-force. The cells are connected one with another by means of fibres, and with muscles, glands, and centres also by means of fibres, which are merely channels for the nerve-force. A stimulus at the surface is carried by a sensory fibre to a cell in the centre; from that point it is carried by another fibre to another cell; and from that by a third fibre to a muscle: a reflex contraction²⁴⁷ results. This is the elementary “nervous arc.” But this arc has also higher arcs with which it is in connection: the sensory cell besides sending a fibre directly to a motor cell, also sends one upwards²⁴⁸ to the cerebral centres; and here again there is300 a nervous arc, so that the cerebral centre sends down an impulse on the motor cells, and the contraction which results is due to a volitional²⁴⁹ impulse. The transmission of the stimulation which in the first case was purely physical, becomes in the latter case psychical²⁵⁰. The sensory impression is in one cell transformed into a sensation, in another cell into an idea, in a third cell into a volition.

150. This course is described with a precision and a confidence which induces the inexperienced reader to suppose that it is the transcript²⁵¹ of actual observation. I venture to say that it is imaginary from beginning to end. I do not affirm that no such course is pursued, I only say no such course was ever demonstrated, but that at every stage the requisite²⁵² facts of observation are either incomplete or contradictory. First, be it noted that the actions to be explained are never the actions of organs so simple as the description sets forth. It is not by single fibres and cells that the stimulus is effected, but by complex nerves and complex centres. Only by a diagrammatic artifice can the fibre represent the nerve, and the cell the centre. In reality the cells of the centre (supposing them to be the only agents) act in groups, and Anatomy should therefore show them to be mutually united in groups—which is what no Anatomy has succeeded in showing, unless the Neuroglia be called upon. Secondly, be it noted that the current scheme of the relations between cells and fibres is one founded on physiological postulates, not on observation. Thirdly, much of what is actually observed is very doubtful, because we do not know whether the appearances are normal, or due to modes of preparation and post-mortem changes. We cannot at present say, for instance, whether the fibrillated appearance of cell contents and axis cylinder represents the living structure or not. We may either suppose that the301 neuroplasmic pulp²⁵³ splits longitudinally into fibres, or that neuroplasmic threads resolve themselves into a homogeneous pulp—the axis cylinder may be a condensation²⁵⁴ of many fibrils, or the fibrils may be a resolution of the substance.

151. Let us contrast step by step the Imaginary Anatomy found in the text-books with the Objective Anatomy as at present disclosed by the researches of all the chief workers. Imaginary Anatomy assumes that the sensory fibre passes from a surface into the cells of the posterior horn of the spinal cord. Objective Anatomy sees the fibre pass into the gray substance, but declares that no direct entrance of a fibre into a cell is there visible.

Imaginary Anatomy assumes that from the sensory cells of the gray substance pass fibres in connection with the motor cells of the anterior horn, thus forming a direct channel through which the excitation of a sensory cell is transmitted to a motor cell. Objective Anatomy fails to discover any such direct channel—no such fibres are demonstrable.

Imaginary Anatomy assumes that from the motor cells issue fibres which descend²⁵⁵ to the muscles and glands, and carry there the motor impulses and the “mandates of the will.” Objective Anatomy fails to find at the utmost more than a probability that these cells are continued as fibres, a probability which is founded on the rare facts of cell processes having been seen extending into the roots of the nerves, and of a cell process having occasionally been seen elsewhere continuous with a dark-bordered fibre. Granting, however, that this probability represents the fact, we have thus only one part of the “nervous arc” which can be said to have been verified.

Imaginary Anatomy further assumes that this nervous arc is connected with cerebral centres by means of fibres going upwards from the posterior cells, and fibres descending302 downwards²⁵⁶ to the anterior cells. Objective Anatomy sees nothing of the kind. It sees fibres entering the gray substance, and there lost to view in a mass of granular substance, fibrils, neuroblasts, and cells. There may be uninterrupted fibres passing upwards and downwards; but it is impossible to see them. And if we are told that physiological interpretations demand such a structure, we may fairly ask if this, and this only, is the structure which is adequate to the propagation of excitation? Now it seems to me that another kind of structure, and one more closely agreeing with what is observed, better answers the demands of Physiology²⁵⁷. This will be more evident after the Laws of Nervous Action have been expounded²⁵⁸ in the succeeding chapter. Meanwhile we may remark that the arrangement of cells and fibres which is imagined as the mechanism²⁵⁹ of propagation and reflexion is absolutely irreconcilable with the teaching of Experiment: for the spinal cord may be cut through anywhere, without destruction of the transmission of sensory and motor excitations, provided only a small portion of gray substance be left to establish the continuity of the axis. Divide all the substance of the posterior half in one place, and all the substance of the anterior half in another, yet so long as there is a portion of gray substance left as a bridge between the lower and upper segments, the transmission of sensory and motor excitations will take place.

152. In other essential respects we have to note that the anatomical evidence for the current interpretations is absolutely deficient or contradictory. There is no adequate warrant for the assumption that all nerves have their origin in ganglia, all fibres in cells. Such evidence as at present exists is against that supposition, and in favor of the supposition that both cell and fibre are differentiations of a common neuroplasm, sometimes directly,303 sometimes indirectly²⁶⁰ continuous. Fibres, and plexuses of fibres, interspersed with cells irregularly distributed—now singly, now in small groups, now in larger and larger groups—constitute the figured elements of nerve-tissue; and even if we set aside the amorphous substance as indifferent or subordinate, we have still no ground for assigning the supremacy²⁶¹, much less the sole significance, to the cells. The grounds of this denial have been amply furnished in our exposition. For, let it be granted that nerve-cells are the origins of the fibres and the sources of their nutrition—a point which is eminently²⁶² disputable—this would in no sense help the physiological hypothesis of the cell as the fountain of Neurility. If the fibre is simply the cell-contents drawn out longitudinally, if its essential element is identical with the essential element of the cell, then we can no more ascribe to the cell the exclusive property of Neurility than we can draw a lump of lead out into a wire, and then ascribe different properties to the thin end and the thick end. But on this point it is needless to speculate, since we have experimental evidence proving that the nerve-fibre has its Neurility even when separated from the cell, or even from the ganglion.

153. It is possible—I do not see sufficient evidence for a stronger assertion—that the cells are the nutritive sources of the fibres. They may represent the alimental rather than the instrumental activities of nervous life. (Compare Problem I. § 42.) My contention²⁶³ is that in any case they are not the supreme elements of the active tissue, and in no sense can they be considered as organs. Only confusion of ideas could for a moment permit such language, or could assign central functions to cells which are elements of tissue. If the cell be credited with such powers anywhere, it must be credited with them everywhere. Now I ask what conceivable central304 function can be ascribed to a cell which terminates the fibre in a peripheral ganglion, or which is merely an enlargement in the course of a fibre in a nerve-bundle? Besides the facts already adduced, let attention be called to this: If a nerve-bundle from the submucosa of the intestine¹⁷ be examined, there appear among the fibres many nuclei (neuroblasts), and occasionally cells, unipolar and bipolar. These cells—if we may trust the observations of Rouget on the earliest development of nerves, and of Sigmund Mayer on regenerated nerves—are simply more advanced stages of evolution of the neuroblasts; but whatever their genesis may be, there can be nothing in the nature of a central function assigned to them.

154. It may be asked, What part can we assign to cells in neural actions if they are apolar, unipolar, and even when multipolar, isolated from each other, and from fibres? I confess that I have no answer ready, not even an hypothesis. Until some rational interpretation of the cell be given we must be content to hold an answer in suspense²⁶⁴. What I would urge is that we are precipitate in assuming that the anatomical connection between one element and another must necessarily be that of a fibre. In a semi-fluid substance, such as neurine, continuity may be perfect without solid fibres: the amorphous substance and the plasmode may as well transmit waves of molecular motion from one part of the tissue to another, and therefore from cell to cell, or from cell to fibre, as a figured substance may. When the posterior root enters the gray substance of the cord, there is no more necessity for its fibres passing directly into the cells of that gray substance, in order to excite their activity, than there is for a wire to pass from the bell to the ear of the servant, who hears the vibrations²⁶⁵ of the bell through the pulsations of the intervening air upon her tympanum. Look at the structure of the retina, or the cerebellum, and you will305 find that the ganglionic cells which have processes passing in a direction contrary to that whence the stimulus arrives, have none where continuity of fibre and cell would be indispensable on the current hypothesis. Light stimulates²⁶⁶ the rods and cones²⁶⁷, but there are no nerve-fibres, hitherto discovered, passing from these to the ganglionic cells; instead of that there is a ground-substance thickly interspersed with granules and nuclei. From the cells we see processes issue; to the cells none are seen arriving. So with the cerebellum. The large cells send their processes upwards to the surface; but downwards towards the white substance the processes are lost in the granular layer, which most histologists regard as connective tissue.

155. A mere glance at nervous tissue in any part will show that cells are far from forming the principal constituents²⁶⁸. In the epidermis²⁶⁹ or a gland¹⁸ the cell is obviously the chief element, forming the bulk of the tissue, and being the characteristic agent. In nerve-tissue, as in connective tissue, the reverse is the case. We must therefore cease to regard the cell as having the importance now attached to it, and must rather throw the emphasis on the fibres and neuroglia.

156. Before quitting this subject let a word be said on the amazing classification which has attained²⁷⁰ wide acceptance (although rejected by the most eminent authorities), founded on the size of the cells—the large multipolar cells being specified²⁷¹ as motor, the smaller cells as sensory, while those of an intermediate size are sympathetic. I forbear to dwell on the development of this notion which specifies²⁷² sensational, ideational, and emotional cells, because this does not pretend to have a basis in observation; whereas there are anatomical facts which give a certain superficial plausibility²⁷³ to the original classification. The conception is profoundly unphysiological; yet, if the anatomical306 evidence were constant, one might give it another interpretation. The evidence is, however, not constant. Large cells are found in regions assigned to sensory nerves, and small cells in motor regions. In the spinal cord of the tortoise Stieda declares that the so-called motor cells are limited to the cervical and lumbar enlargements; all the rest of the motor region being absolutely destitute of them.182 Again look at the cells of the retina—no one will assign motor functions to them—yet they are the same as those of the cerebellum and the anterior horns of the spinal cord. (It is worth a passing mention that the structure of the nervous parts of the retina more closely resembles that of the cerebellum than of the cerebrum.)

157. While our knowledge of the cell is thus far indeed from having the precision which the text-books display, and in no sense warrants the current physiological interpretations, our knowledge of fibres and neuroglia is also too incomplete for theoretic purposes. We know that the axis cylinder is the essential element; but we are still at a loss what part is to be assigned to the medullary sheath. There is indeed a popular hypothesis which pronounces it to be the means of insulating the fibre, and thus preserving the isolated conduction of nerve-force. Being of a fatty nature, this insulating office was readily suggested in agreement with the assumption that Neurility was Electricity. Now, without discussing whether Neurility is or is not Electricity, even admitting the former to be satisfactorily proved, I must remark that the admission still leaves the medullary sheath incapable²⁷⁴ of fulfilling the supposed office, since not only is there no such sheath in most of the invertebrates and in the sympathetic nerves of vertebrates, but even in those nerves which have the sheath it is precisely²⁷⁵ in places where the307 insulation²⁷⁶ would be most needed—namely, just before the terminations of the fibres in muscles and in centres—that the sheath is absent. This is as if we tried to conduct water through a pipe which fell short at both ends—before it left the cistern²⁷⁷, and before it reached the spot to be watered. If there is a tendency in Neurility to spread wherever it is not insulated by a medullary sheath, then before reaching the centres and the muscles, it must, on the insulating hypothesis, dribble²⁷⁸ away!

158. The facts expressed in the “law of isolated conduction” are important, and are difficult of explanation; but it is obvious that they cannot be referred to the presence of the medullary sheath. Nor indeed will any insight into the propagation of stimulation through the central axis be intelligible²⁷⁹ until we have reformed our anatomical theories, and taken the Neuroglia into account. The theory which connects every fibre directly with a cell, and every cell with another by anastomosis—even were it demonstrated—would not explain the law of isolated conduction. Butzke cogently²⁸⁰ remarks183 that such a disposition of the elements should render all neural paths invariable; whereas the fact is that they are very variable. We learn to perform actions, and then we unlearn them; the paths are traversed now in one direction, now in another. Fluctuation is the characteristic of central combinations. And for this fluctuating combination of elements a corresponding diversity is required in the possible channels. This seems to be furnished by the network of the Neuroglia. See the representation copied from Butzke’s plate, and note how the cell-process blends with the meshes of the Neuroglia. Is it fanciful to regard this network of fibrils as having somewhat the relation of capillaries²⁸¹ to blood-vessels? Did we not experimentally308 know that the capillaries are terminal blood-vessels, we should not suspect it from mere examination of the structure.

159. Having insisted that our knowledge is insufficient²⁸² for any explanation of the “law of isolated conduction,” I can only suggest a path of research which may lead to some result. What we know is that some stimulations are propagated from one end of the cerebro-spinal axis to the other in definitely restricted paths, while others are irradiated along many paths. In the succeeding chapter this will be more fully²⁸³ considered; what we have here to note is that the manifold irradiations of a stimulation have an anatomical substratum in the manifold sub-divisions of the network of fibrils and the amorphous substance in which they penetrate²⁸⁴.

 

Fig. 26.—Nerve-cells with processes terminating in neuroglia.

160. In conclusion, I would say, let no one place a too great confidence in the reigning doctrines²⁸⁵ respecting the elementary structure of the nervous system, but accept every statement as a “working hypothesis” which has its value in so far as it links together verified facts, or309 suggests new research, but is wholly without value in so far as it is made a basis of deductions not otherwise verified. Hypotheses are indispensable to research, but they must be accompanied by vigilant scepticism. Imagination is only an enemy to Science when Scepticism is asleep.

1 investigation   

n.调查，调查研究

参考例句：

• In an investigation,a new fact became known, which told against him.在调查中新发现了一件对他不利的事实。
• He drew the conclusion by building on his own investigation.他根据自己的调查研究作出结论。

2 phenomena   

n.现象

参考例句：

• Ade couldn't relate the phenomena with any theory he knew.艾德无法用他所知道的任何理论来解释这种现象。
• The object of these experiments was to find the connection,if any,between the two phenomena.这些实验的目的就是探索这两种现象之间的联系，如果存在着任何联系的话。

3 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

4 component   

n.组成部分，成分，元件；adj.组成的，合成的

参考例句：

• Each component is carefully checked before assembly.每个零件在装配前都经过仔细检查。
• Blade and handle are the component parts of a knife.刀身和刀柄是一把刀的组成部分。

5 analytical   

adj.分析的；用分析法的

参考例句：

• I have an analytical approach to every survey.对每项调查我都采用分析方法。
• As a result,analytical data obtained by analysts were often in disagreement.结果各个分析家所得的分析数据常常不一致。

6 beset   

v.镶嵌；困扰，包围

参考例句：

• She wanted to enjoy her retirement without being beset by financial worries.她想享受退休生活而不必为金钱担忧。
• The plan was beset with difficulties from the beginning.这项计划自开始就困难重重。

7 artifice   

n.妙计，高明的手段；狡诈，诡计

参考例句：

• The use of mirrors in a room is an artifice to make the room look larger.利用镜子装饰房间是使房间显得大一点的巧妙办法。
• He displayed a great deal of artifice in decorating his new house.他在布置新房子中表现出富有的技巧。

8 reconstruction   

n.重建，再现，复原

参考例句：

• The country faces a huge task of national reconstruction following the war.战后，该国面临着重建家园的艰巨任务。
• In the period of reconstruction,technique decides everything.在重建时期，技术决定一切。

9 superstition   

n.迷信，迷信行为

参考例句：

• It's a common superstition that black cats are unlucky.认为黑猫不吉祥是一种很普遍的迷信。
• Superstition results from ignorance.迷信产生于无知。

10 usurped   

篡夺，霸占( usurp的过去式和过去分词 )； 盗用； 篡夺，篡权

参考例句：

• That magazine usurped copyrighted material. 那杂志盗用了版权为他人所有的素材。
• The expression'social engineering'has been usurped by the Utopianist without a shadow of light. “社会工程”这个词已被乌托邦主义者毫无理由地盗用了。

11 usurp   

vt.篡夺，霸占；vi.篡位

参考例句：

• Their position enabled them to usurp power.他们所处的地位使其得以篡权。
• You must not allow it to usurp a disproportionate share of your interest.你不应让它过多地占据你的兴趣。

12 physiologists   

n.生理学者( physiologist的名词复数 )；生理学( physiology的名词复数 )；生理机能

参考例句：

• Quite unexpectedly, vertebrate physiologists and microbial biochemists had found a common ground. 出乎意外，脊椎动物生理学家和微生物生化学家找到了共同阵地。 来自辞典例句
• Physiologists are interested in the workings of the human body. 生理学家对人体的功能感兴趣。 来自辞典例句

13 physiologist   

n.生理学家

参考例句：

• Russian physiologist who observed conditioned salivary responses in dogs (1849-1936). （1849-1936）苏联生理学家，在狗身上观察到唾液条件反射，曾获1904年诺贝尔生理学-医学奖。
• The physiologist recently studied indicated that evening exercises beneficially. 生理学家新近研究表明，傍晚锻炼最为有益。

14 interpretations   

n.解释( interpretation的名词复数 )；表演；演绎；理解

参考例句：

• This passage is open to a variety of interpretations. 这篇文章可以有各种不同的解释。 来自《简明英汉词典》
• The involved and abstruse passage makes several interpretations possible. 这段艰涩的文字可以作出好几种解释。 来自《现代汉英综合大词典》

15 interpretation   

n.解释，说明，描述；艺术处理

参考例句：

• His statement admits of one interpretation only.他的话只有一种解释。
• Analysis and interpretation is a very personal thing.分析与说明是个很主观的事情。

16 intestines   

n.肠( intestine的名词复数 )

参考例句：

• Perhaps the most serious problems occur in the stomach and intestines. 最严重的问题或许出现在胃和肠里。 来自辞典例句
• The traps of carnivorous plants function a little like the stomachs and small intestines of animals. 食肉植物的捕蝇器起着动物的胃和小肠的作用。 来自辞典例句

17 intestine   

adj.内部的；国内的；n.肠

参考例句：

• This vitamin is absorbed through the walls of the small intestine.这种维生素通过小肠壁被吸收。
• The service productivity is the function,including external efficiency,intestine efficiency and capacity efficiency.服务业的生产率是一个包含有外部效率、内部效率和能力效率的函数。

18 gland   

n.腺体，(机)密封压盖，填料盖

参考例句：

• This is a snake's poison gland.这就是蛇的毒腺。
• Her mother has an underactive adrenal gland.她的母亲肾上腺机能不全。

19 glands   

n.腺( gland的名词复数 )

参考例句：

• a snake's poison glands 蛇的毒腺
• the sebaceous glands in the skin 皮脂腺

20 vessels   

n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人

参考例句：

• The river is navigable by vessels of up to 90 tons. 90 吨以下的船只可以从这条河通过。 来自《简明英汉词典》
• All modern vessels of any size are fitted with radar installations. 所有现代化船只都有雷达装置。 来自《现代汉英综合大词典》

21 radical   

n.激进份子，原子团，根号；adj.根本的，激进的，彻底的

参考例句：

• The patient got a radical cure in the hospital.病人在医院得到了根治。
• She is radical in her demands.她的要求十分偏激。

22 physiological   

adj.生理学的，生理学上的

参考例句：

• He bought a physiological book.他买了一本生理学方面的书。
• Every individual has a physiological requirement for each nutrient.每个人对每种营养成分都有一种生理上的需要。

23 speculation   

n.思索，沉思；猜测；投机

参考例句：

• Her mind is occupied with speculation.她的头脑忙于思考。
• There is widespread speculation that he is going to resign.人们普遍推测他要辞职。

24 incessantly   

ad.不停地

参考例句：

• The machines roar incessantly during the hours of daylight. 机器在白天隆隆地响个不停。
• It rained incessantly for the whole two weeks. 雨不间断地下了整整两个星期。

25 sarcasm   

n.讥讽，讽刺，嘲弄，反话 （adj.sarcastic）

参考例句：

• His sarcasm hurt her feelings.他的讽刺伤害了她的感情。
• She was given to using bitter sarcasm.她惯于用尖酸刻薄语言挖苦人。

26 microscopic   

adj.微小的，细微的，极小的，显微的

参考例句：

• It's impossible to read his microscopic handwriting.不可能看清他那极小的书写字迹。
• A plant's lungs are the microscopic pores in its leaves.植物的肺就是其叶片上微细的气孔。

27 ardor   

n.热情，狂热

参考例句：

• His political ardor led him into many arguments.他的政治狂热使他多次卷入争论中。
• He took up his pursuit with ardor.他满腔热忱地从事工作。

28 precipitate   

adj.突如其来的；vt.使突然发生；n.沉淀物

参考例句：

• I don't think we should make precipitate decisions.我认为我们不应该贸然作出决定。
• The king was too precipitate in declaring war.国王在宣战一事上过于轻率。

29 monographs   

n.专著，专论( monograph的名词复数 )

参考例句：

• The scholarly monographs were published as pamphlet. 学术专著是以小册子形式出版的。 来自《简明英汉词典》
• Subsequent individual monographs will proceed at increasing levels of sophistication. 此后几集将继续提高论述水平。 来自辞典例句

30 tavern   

n.小旅馆，客栈；小酒店

参考例句：

• There is a tavern at the corner of the street.街道的拐角处有一家酒馆。
• Philip always went to the tavern,with a sense of pleasure.菲利浦总是心情愉快地来到这家酒菜馆。

31 potent   

adj.强有力的，有权势的；有效力的

参考例句：

• The medicine had a potent effect on your disease.这药物对你的病疗效很大。
• We must account of his potent influence.我们必须考虑他的强有力的影响。

32 scattered   

adj.分散的，稀疏的；散步的；疏疏落落的

参考例句：

• Gathering up his scattered papers,he pushed them into his case.他把散乱的文件收拾起来，塞进文件夹里。

33 corks   

n.脐梅衣；软木( cork的名词复数 )；软木塞

参考例句：

• Champagne corks were popping throughout the celebrations. 庆祝会上开香槟酒瓶塞的砰砰声不绝於耳。 来自辞典例句
• Champagne corks popped, and on lace tablecloths seven-course dinners were laid. 桌上铺着带装饰图案的网织的桌布，上面是七道菜的晚餐。 来自飘（部分）

34 intelligibly   

adv.可理解地，明了地，清晰地

参考例句：

• The foreigner spoke to us quite intelligibly. 这个外国人对我们讲的话理解很好。 来自《简明英汉词典》
• Logically or intelligibly ordered or presented; coherent. 有逻辑或理性地排列或表现的；协调的。 来自互联网

35 wary   

adj.谨慎的，机警的，小心的

参考例句：

• He is wary of telling secrets to others.他谨防向他人泄露秘密。
• Paula frowned,suddenly wary.宝拉皱了皱眉头，突然警惕起来。

36 demonstration   

n.表明，示范，论证，示威

参考例句：

• His new book is a demonstration of his patriotism.他写的新书是他的爱国精神的证明。
• He gave a demonstration of the new technique then and there.他当场表演了这种新的操作方法。

37 vice   

n.坏事；恶习；[pl.]台钳，老虎钳；adj.副的

参考例句：

• He guarded himself against vice.他避免染上坏习惯。
• They are sunk in the depth of vice.他们堕入了罪恶的深渊。

38 postulates   

v.假定，假设( postulate的第三人称单数 )

参考例句：

• They proclaimed to be eternal postulates of reason and justice. 他们宣称这些原则是理性和正义的永恒的要求。 来自辞典例句
• The school building programme postulates an increase in educational investment. 修建校舍的计画是在增加教育经费的前提下拟定的。 来自辞典例句

39 postulate   

n.假定，基本条件；vt.要求，假定

参考例句：

• Let's postulate that she is a cook.我们假定她是一位厨师。
• Freud postulated that we all have a death instinct as well as a life instinct.弗洛伊德曾假定我们所有人都有生存本能和死亡本能。

40 isolated   

adj.与世隔绝的

参考例句：

• His bad behaviour was just an isolated incident. 他的不良行为只是个别事件。
• Patients with the disease should be isolated. 这种病的患者应予以隔离。

41 periphery   

n.(圆体的)外面；周围

参考例句：

• Geographically, the UK is on the periphery of Europe.从地理位置上讲，英国处于欧洲边缘。
• The periphery of the retina is very sensitive to motion.视网膜的外围对运动非常敏感。

42 deduction   

n.减除，扣除，减除额；推论，推理，演绎

参考例句：

• No deduction in pay is made for absence due to illness.因病请假不扣工资。
• His deduction led him to the correct conclusion.他的推断使他得出正确的结论。

43 nay   

adv.不；n.反对票，投反对票者

参考例句：

• He was grateful for and proud of his son's remarkable,nay,unique performance.他为儿子出色的，不，应该是独一无二的表演心怀感激和骄傲。
• Long essays,nay,whole books have been written on this.许多长篇大论的文章，不，应该说是整部整部的书都是关于这件事的。

44 lengthy   

adj.漫长的，冗长的

参考例句：

• We devoted a lengthy and full discussion to this topic.我们对这个题目进行了长时间的充分讨论。
• The professor wrote a lengthy book on Napoleon.教授写了一部有关拿破仑的巨著。

45 sensory   

adj.知觉的，感觉的，知觉器官的

参考例句：

• Human powers of sensory discrimination are limited.人类感官分辨能力有限。
• The sensory system may undergo long-term adaptation in alien environments.感觉系统对陌生的环境可能经过长时期才能适应。

46 spinal   

adj.针的，尖刺的，尖刺状突起的；adj.脊骨的，脊髓的

参考例句：

• After three days in Japan,the spinal column becomes extraordinarily flexible.在日本三天，就已经使脊椎骨变得富有弹性了。
• Your spinal column is made up of 24 movable vertebrae.你的脊柱由24个活动的脊椎骨构成。

47 anterior   

adj.较早的；在前的

参考例句：

• We've already finished the work anterior to the schedule.我们已经提前完成了工作。
• The anterior part of a fish contains the head and gills.鱼的前部包括头和鳃。

48 anatomy   

n.解剖学，解剖；功能，结构，组织

参考例句：

• He found out a great deal about the anatomy of animals.在动物解剖学方面，他有过许多发现。
• The hurricane's anatomy was powerful and complex.对飓风的剖析是一项庞大而复杂的工作。

49 relinquish   

v.放弃，撤回，让与，放手

参考例句：

• He was forced to relinquish control of the company.他被迫放弃公司的掌控权。
• They will never voluntarily relinquish their independence.他们绝对不会自动放弃独立。

50 plausible   

adj.似真实的，似乎有理的，似乎可信的

参考例句：

• His story sounded plausible.他说的那番话似乎是真实的。
• Her story sounded perfectly plausible.她的说辞听起来言之有理。

51 speculations   

n.投机买卖( speculation的名词复数 )；思考；投机活动；推断

参考例句：

• Your speculations were all quite close to the truth. 你的揣测都很接近于事实。 来自《现代英汉综合大词典》
• This possibility gives rise to interesting speculations. 这种可能性引起了有趣的推测。 来自《用法词典》

52 asunder   

adj.分离的，化为碎片

参考例句：

• The curtains had been drawn asunder.窗帘被拉向两边。
• Your conscience,conviction,integrity,and loyalties were torn asunder.你的良心、信念、正直和忠诚都被扯得粉碎了。

53 embedded   

a.扎牢的

参考例句：

• an operation to remove glass that was embedded in his leg 取出扎入他腿部玻璃的手术
• He has embedded his name in the minds of millions of people. 他的名字铭刻在数百万人民心中。

54 constituent   

n.选民；成分，组分；adj.组成的，构成的

参考例句：

• Sugar is the main constituent of candy.食糖是糖果的主要成分。
• Fibre is a natural constituent of a healthy diet.纤维是健康饮食的天然组成部分。

55 alteration   

n.变更，改变；蚀变

参考例句：

• The shirt needs alteration.这件衬衣需要改一改。
• He easily perceived there was an alteration in my countenance.他立刻看出我的脸色和往常有些不同。

56 deformed   

adj.畸形的；变形的；丑的，破相了的

参考例句：

• He was born with a deformed right leg.他出生时右腿畸形。
• His body was deformed by leprosy.他的身体因为麻风病变形了。

57 nucleus   

n.核，核心，原子核

参考例句：

• These young people formed the nucleus of the club.这些年轻人成了俱乐部的核心。
• These councils would form the nucleus of a future regime.这些委员会将成为一个未来政权的核心。

58 embryo   

n.胚胎，萌芽的事物

参考例句：

• They are engaging in an embryo research.他们正在进行一项胚胎研究。
• The project was barely in embryo.该计划只是个雏形。

59 embryonic   

adj.胚胎的

参考例句：

• It is still in an embryonic stage.它还处于萌芽阶段。
• The plan,as yet,only exists in embryonic form.这个计划迄今为止还只是在酝酿之中。

60 applied   

adj.应用的；v.应用，适用

参考例句：

• She plans to take a course in applied linguistics.她打算学习应用语言学课程。
• This cream is best applied to the face at night.这种乳霜最好晚上擦脸用。

61 variance   

n.矛盾，不同

参考例句：

• The question of woman suffrage sets them at variance. 妇女参政的问题使他们发生争执。
• It is unnatural for brothers to be at variance. 兄弟之间不睦是不近人情的。

62 isolation   

n.隔离，孤立，分解，分离

参考例句：

• The millionaire lived in complete isolation from the outside world.这位富翁过着与世隔绝的生活。
• He retired and lived in relative isolation.他退休后，生活比较孤寂。

63 textural   

adj. 组织上的, 构造上的

参考例句：

• the textural characteristics of the rocks 岩石的纹理特征
• High solid ferments and yeast lees contract to highlight textural qualities. 采用固体发和酵母分离技术提高酒的品质。

64 rim   

n.(圆物的)边，轮缘；边界

参考例句：

• The water was even with the rim of the basin.盆里的水与盆边平齐了。
• She looked at him over the rim of her glass.她的目光越过玻璃杯的边沿看着他。

65 weir   

n.堰堤，拦河坝

参考例句：

• The discharge from the weir opening should be free.从堰开口处的泻水应畅通。
• Big Weir River,restraining tears,has departed!大堰河，含泪地去了！

66 thawed   

解冻

参考例句：

• The little girl's smile thawed the angry old man. 小姑娘的微笑使发怒的老头缓和下来。 来自《简明英汉词典》
• He thawed after sitting at a fire for a while. 在火堆旁坐了一会儿，他觉得暖和起来了。 来自《简明英汉词典》

67 delicacy   

n.精致，细微，微妙，精良；美味，佳肴

参考例句：

• We admired the delicacy of the craftsmanship.我们佩服工艺师精巧的手艺。
• He sensed the delicacy of the situation.他感觉到了形势的微妙。

68 determined   

adj.坚定的；有决心的

参考例句：

• I have determined on going to Tibet after graduation.我已决定毕业后去西藏。
• He determined to view the rooms behind the office.他决定查看一下办公室后面的房间。

69 mere   

adj.纯粹的；仅仅，只不过

参考例句：

• That is a mere repetition of what you said before.那不过是重复了你以前讲的话。
• It's a mere waste of time waiting any longer.再等下去纯粹是浪费时间。

70 secondly   

adv.第二，其次

参考例句：

• Secondly,use your own head and present your point of view.第二，动脑筋提出自己的见解。
• Secondly it is necessary to define the applied load.其次，需要确定所作用的载荷。

71 amorphous   

adj.无定形的

参考例句：

• There was a weakening of the intermolecular bonds,primarily in the amorphous region of the polymer.分子间键合减弱，尤其在聚合物的无定形区内更为明显。
• It is an amorphous colorless or white powder.它是一种无定形的无色或白色粉末。

72 enumeration   

n.计数，列举；细目；详表；点查

参考例句：

• Predictive Categoriesinclude six categories of prediction, namely Enumeration, Advance Labeling, Reporting,Recapitulation, Hypotheticality, and Question. 其中预设种类又包括列举(Enumeration)、提前标示(Advance Labeling)、转述(Reporting)、回顾(Recapitulation)、假设(Hypotheticality)和提问(Question)。 来自互联网
• Here we describe a systematic procedure which is basically "enumeration" in nature. 这里介绍一个本质上是属于“枚举法”的系统程序。 来自辞典例句

73 vigilant   

adj.警觉的，警戒的，警惕的

参考例句：

• He has to learn how to remain vigilant through these long nights.他得学会如何在这漫长的黑夜里保持警觉。
• The dog kept a vigilant guard over the house.这只狗警醒地守护着这所房屋。

74 sufficiently   

adv.足够地，充分地

参考例句：

• It turned out he had not insured the house sufficiently.原来他没有给房屋投足保险。
• The new policy was sufficiently elastic to accommodate both views.新政策充分灵活地适用两种观点。

75 fig   

n.无花果(树)

参考例句：

• The doctor finished the fig he had been eating and selected another.这位医生吃完了嘴里的无花果，又挑了一个。
• You can't find a person who doesn't know fig in the United States.你找不到任何一个在美国的人不知道无花果的。

76 relegated   

v.使降级( relegate的过去式和过去分词 )；使降职；转移；把…归类

参考例句：

• She was then relegated to the role of assistant. 随后她被降级做助手了。
• I think that should be relegated to the garbage can of history. 我认为应该把它扔进历史的垃圾箱。 来自《现代汉英综合大词典》

77 generic   

adj.一般的，普通的，共有的

参考例句：

• I usually buy generic clothes instead of name brands.我通常买普通的衣服，不买名牌。
• The generic woman appears to have an extraordinary faculty for swallowing the individual.一般妇女在婚后似乎有特别突出的抑制个性的能力。

78 infancy   

n.婴儿期；幼年期；初期

参考例句：

• He came to England in his infancy.他幼年时期来到英国。
• Their research is only in its infancy.他们的研究处于初级阶段。

79 conspicuous   

adj.明眼的，惹人注目的；炫耀的，摆阔气的

参考例句：

• It is conspicuous that smoking is harmful to health.很明显，抽烟对健康有害。
• Its colouring makes it highly conspicuous.它的色彩使它非常惹人注目。

80 nuclei   

n.核

参考例句：

• To free electrons, something has to make them whirl fast enough to break away from their nuclei. 为了释放电子，必须使电子高速旋转而足以摆脱原子核的束缚。
• Energy is released by the fission of atomic nuclei. 能量是由原子核分裂释放出来的。

81 striated   

adj.有纵线，条纹的

参考例句：

• The striated and polished surfaces are called slicken-sides.有条痕的磨光面则称为擦痕面。
• There are striated engravings on this wall.这面墙上有着条纹状的雕饰。

82 diffused   

散布的，普及的，扩散的

参考例句：

• A drop of milk diffused in the water. 一滴牛奶在水中扩散开来。
• Gases and liquids diffused. 气体和液体慢慢混合了。

83 pigment   

n.天然色素，干粉颜料

参考例句：

• The Romans used natural pigments on their fabrics and walls.古罗马人在织物和墙壁上使用天然颜料。
• Who thought he might know what the skin pigment phenomenon meant.他自认为可能知道皮肤色素出现这种现象到底是怎么回事。

84 axis   

n.轴，轴线，中心线；坐标轴，基准线

参考例句：

• The earth's axis is the line between the North and South Poles.地轴是南北极之间的线。
• The axis of a circle is its diameter.圆的轴线是其直径。

85 cylinder   

n.圆筒，柱(面)，汽缸

参考例句：

• What's the volume of this cylinder?这个圆筒的体积有多少？
• The cylinder is getting too much gas and not enough air.汽缸里汽油太多而空气不足。

86 calf   

n.小牛，犊，幼仔，小牛皮

参考例句：

• The cow slinked its calf.那头母牛早产了一头小牛犊。
• The calf blared for its mother.牛犊哞哞地高声叫喊找妈妈。

87 interspersed   

adj.[医]散开的；点缀的v.intersperse的过去式和过去分词

参考例句：

• Lectures will be interspersed with practical demonstrations. 讲课中将不时插入实际示范。
• The grass was interspersed with beds of flowers. 草地上点缀着许多花坛。 来自《现代英汉综合大词典》

88 positively   

adv.明确地，断然，坚决地；实在，确实

参考例句：

• She was positively glowing with happiness.她满脸幸福。
• The weather was positively poisonous.这天气着实讨厌。

89 withdrawn   

vt.收回；使退出；vi.撤退，退出

参考例句：

• Our force has been withdrawn from the danger area.我们的军队已从危险地区撤出。
• All foreign troops should be withdrawn to their own countries.一切外国军队都应撤回本国去。

90 drawn   

v.拖，拉，拔出；adj.憔悴的，紧张的

参考例句：

• All the characters in the story are drawn from life.故事中的所有人物都取材于生活。
• Her gaze was drawn irresistibly to the scene outside.她的目光禁不住被外面的风景所吸引。

91 coagulation   

n.凝固；凝结物

参考例句：

• Blood becomes stickier to help coagulation in case of a cut.割伤的时候，血液会变得更为黏稠以助于凝结。
• Man has been intrigued with blood coagulation.人类一直对血凝感兴趣。

92 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。

93 serum   

n.浆液，血清，乳浆

参考例句：

• The serum is available to the general public.一般公众均可获得血清。
• Untreated serum contains a set of 11 proteins called complement.未经处理的血清含有一组蛋白质，共11种，称为补体。

94 transparent   

adj.明显的，无疑的；透明的

参考例句：

• The water is so transparent that we can see the fishes swimming.水清澈透明，可以看到鱼儿游来游去。
• The window glass is transparent.窗玻璃是透明的。

95 entangled   

adj.卷入的；陷入的；被缠住的；缠在一起的v.使某人（某物/自己）缠绕，纠缠于（某物中），使某人（自己）陷入（困难或复杂的环境中）( entangle的过去式和过去分词 )

参考例句：

• The bird had become entangled in the wire netting. 那只小鸟被铁丝网缠住了。
• Some military observers fear the US could get entangled in another war. 一些军事观察家担心美国会卷入另一场战争。 来自《简明英汉词典》

96 robin   

n.知更鸟，红襟鸟

参考例句：

• The robin is the messenger of spring.知更鸟是报春的使者。
• We knew spring was coming as we had seen a robin.我们看见了一只知更鸟，知道春天要到了。

97 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

98 perishable   

adj.（尤指食物）易腐的，易坏的

参考例句：

• Many fresh foods are highly perishable.许多新鲜食物都极易腐败。
• Fruits are perishable in transit.水果在运送时容易腐烂。

99 cuttlefish   

n.乌贼，墨鱼

参考例句：

• I have no idea about how to prepare those cuttlefish and lobsters.我对如何烹调那些乌贼和龙虾毫无概念。
• The cuttlefish spurts out dark ink when it is in danger.乌鲗遇到危险的时候会喷出黑色液体。

100 wrought   

v.引起；以…原料制作；运转；adj.制造的

参考例句：

• Events in Paris wrought a change in British opinion towards France and Germany.巴黎发生的事件改变了英国对法国和德国的看法。
• It's a walking stick with a gold head wrought in the form of a flower.那是一个金质花形包头的拐杖。

101 hue   

n.色度；色调；样子

参考例句：

• The diamond shone with every hue under the sun.金刚石在阳光下放出五颜六色的光芒。
• The same hue will look different in different light.同一颜色在不同的光线下看起来会有所不同。

102 uncertainty   

n.易变，靠不住，不确知，不确定的事物

参考例句：

• Her comments will add to the uncertainty of the situation.她的批评将会使局势更加不稳定。
• After six weeks of uncertainty,the strain was beginning to take its toll.6个星期的忐忑不安后，压力开始产生影响了。

103 hovers   

鸟( hover的第三人称单数 )； 靠近（某事物）； （人）徘徊； 犹豫

参考例句：

• A hawk hovers in the sky. 一只老鹰在天空盘旋。
• A hen hovers her chicks. 一只母鸡在孵小鸡。

104 uncertainties   

无把握( uncertainty的名词复数 )； 不确定； 变化不定； 无把握、不确定的事物

参考例句：

• One of the uncertainties of military duty is that you never know when you might suddenly get posted away. 任军职不稳定的因素之一是你永远不知道什么时候会突然被派往它处。
• Uncertainties affecting peace and development are on the rise. 影响和平与发展的不确定因素在增加。 来自汉英非文学 - 十六大报告

105 override   

vt.不顾，不理睬，否决；压倒，优先于

参考例句：

• The welfare of a child should always override the wishes of its parents.孩子的幸福安康应该永远比父母的愿望来得更重要。
• I'm applying in advance for the authority to override him.我提前申请当局对他进行否决。

106 generalization   

n.普遍性，一般性，概括

参考例句：

• This sweeping generalization is the law of conservation of energy.这一透彻的概括就是能量守恒定律。
• The evaluation of conduct involves some amount of generalization.对操行的评价会含有一些泛泛之论。

107 neural   

adj.神经的，神经系统的

参考例句：

• The neural network can preferably solve the non- linear problem.利用神经网络建模可以较好地解决非线性问题。
• The information transmission in neural system depends on neurotransmitters.信息传递的神经途径有赖于神经递质。

108 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

109 pliant   

adj.顺从的；可弯曲的

参考例句：

• She's proud and stubborn,you know,under that pliant exterior.你要知道，在温顺的外表下，她既自傲又固执。
• They weave a basket out of osiers with pliant young willows.他们用易弯的柳枝编制篮子。

110 justification   

n.正当的理由；辩解的理由

参考例句：

• There's no justification for dividing the company into smaller units. 没有理由把公司划分成小单位。
• In the young there is a justification for this feeling. 在年轻人中有这种感觉是有理由的。

111 subdivide   

vt.细分（细区分，再划分，重分，叠分，分小类）

参考例句：

• You can use sales organizations to subdivide markets into regions.用销售组织将市场细分为区域。
• The verbs were subdivided into transitive and intransitive categories.动词可细分为及物动词和不及物动词。

112 abound   

vi.大量存在；(in，with)充满，富于

参考例句：

• Oranges abound here all the year round.这里一年到头都有很多橙子。
• But problems abound in the management of State-owned companies.但是在国有企业的管理中仍然存在不少问题。

113 propounded   

v.提出（问题、计划等）供考虑[讨论]，提议( propound的过去式和过去分词 )

参考例句：

• the theory of natural selection, first propounded by Charles Darwin 查尔斯∙达尔文首先提出的物竞天择理论
• Indeed it was first propounded by the ubiquitous Thomas Young. 实际上，它是由尽人皆知的杨氏首先提出来的。 来自辞典例句

114 subdivided   

再分，细分( subdivide的过去式和过去分词 )

参考例句：

• The compound was subdivided into four living areas. 那个区域被划分成4个居住小区。
• This part of geologic calendar has not been satisfactorily subdivided. 这部分地质年代表还没有令人满意地再细分出来。

115 hesitation   

n.犹豫，踌躇

参考例句：

• After a long hesitation, he told the truth at last.踌躇了半天，他终于直说了。
• There was a certain hesitation in her manner.她的态度有些犹豫不决。

116 specially   

adv.特定地；特殊地；明确地

参考例句：

• They are specially packaged so that they stack easily.它们经过特别包装以便于堆放。
• The machine was designed specially for demolishing old buildings.这种机器是专为拆毁旧楼房而设计的。

117 professes   

声称( profess的第三人称单数 )； 宣称； 公开表明； 信奉

参考例句：

• She still professes her innocence. 她仍然声称自己无辜。
• He professes himself to be sad but doesn't look it. 他自称感到悲伤，但外表却看不出来。

118 contradictory   

adj.反驳的，反对的，抗辩的；n.正反对，矛盾对立

参考例句：

• The argument is internally contradictory.论据本身自相矛盾。
• What he said was self-contradictory.他讲话前后不符。

119 stimulus   

n.刺激，刺激物，促进因素，引起兴奋的事物

参考例句：

• Regard each failure as a stimulus to further efforts.把每次失利看成对进一步努力的激励。
• Light is a stimulus to growth in plants.光是促进植物生长的一个因素。

120 eminent   

adj.显赫的，杰出的，有名的，优良的

参考例句：

• We are expecting the arrival of an eminent scientist.我们正期待一位著名科学家的来访。
• He is an eminent citizen of China.他是一个杰出的中国公民。

121 insignificant   

adj.无关紧要的，可忽略的，无意义的

参考例句：

• In winter the effect was found to be insignificant.在冬季，这种作用是不明显的。
• This problem was insignificant compared to others she faced.这一问题与她面临的其他问题比较起来算不得什么。

122 ramifications   

n.结果，后果( ramification的名词复数 )

参考例句：

• These changes are bound to have widespread social ramifications. 这些变化注定会造成许多难以预料的社会后果。
• What are the ramifications of our decision to join the union? 我们决定加入工会会引起哪些后果呢？ 来自《简明英汉词典》

123 conversion   

n.转化，转换，转变

参考例句：

• He underwent quite a conversion.他彻底变了。
• Waste conversion is a part of the production process.废物处理是生产过程的一个组成部分。

124 beheld   

v.看，注视( behold的过去式和过去分词 )；瞧；看呀；（叙述中用于引出某人意外的出现）哎哟

参考例句：

• His eyes had never beheld such opulence. 他从未见过这样的财富。 来自《简明英汉词典》
• The soul beheld its features in the mirror of the passing moment. 灵魂在逝去的瞬间的镜子中看到了自己的模样。 来自英汉文学 - 红字

125 premises   

n.建筑物，房屋

参考例句：

• According to the rules,no alcohol can be consumed on the premises.按照规定，场内不准饮酒。
• All repairs are done on the premises and not put out.全部修缮都在家里进行，不用送到外面去做。

126 unstable   

adj.不稳定的，易变的

参考例句：

• This bookcase is too unstable to hold so many books.这书橱很不结实，装不了这么多书。
• The patient's condition was unstable.那患者的病情不稳定。

127 functional   

adj.为实用而设计的，具备功能的，起作用的

参考例句：

• The telephone was out of order,but is functional now.电话刚才坏了，但现在可以用了。
• The furniture is not fancy,just functional.这些家具不是摆着好看的，只是为了实用。

128 hesitations   

n.犹豫( hesitation的名词复数 )；踌躇；犹豫（之事或行为）；口吃

参考例句：

• His doubts and hesitations were tiresome. 他的疑惑和犹豫令人厌烦。 来自《简明英汉词典》
• The cool manipulators in Hanoi had exploited America's hesitations and self-doubt. 善于冷静地操纵这类事的河内统治者大大地钻了美国当局优柔寡断的空子。 来自辞典例句

129 membranous   

adj.膜的，膜状的

参考例句：

• Others are born live, after struggling to break free from a membranous egg sac. 其余的是冲破膜状蛋囊而出生的。 来自电影对白
• Thellos thellon, membranous layer of life is our only home. 薄薄的膜层就是咱们独一的家园。 来自互联网

130 annular   

adj.环状的

参考例句：

• It was reported that there would be an annular eclipse tomorrow.据报道说，明天有日环食。
• The annular markings on a tree indicate its age.树的环形纹理显示其年龄。

131 constriction   

压缩； 紧压的感觉； 束紧； 压缩物

参考例句：

• She feels a constriction in the chest. 她胸部有压迫感。
• If you strain to run fast, you start coughing and feel a constriction in the chest. 还是别跑紧了，一咬牙就咳嗽，心口窝辣蒿蒿的！ 来自汉英文学 - 骆驼祥子

132 intervals   

n.[军事]间隔( interval的名词复数 )；间隔时间；[数学]区间；（戏剧、电影或音乐会的）幕间休息

参考例句：

• The forecast said there would be sunny intervals and showers. 预报间晴，有阵雨。
• Meetings take place at fortnightly intervals. 每两周开一次会。

133 thereby   

adv.因此，从而

参考例句：

• I have never been to that city,,ereby I don't know much about it.我从未去过那座城市，因此对它不怎么熟悉。
• He became a British citizen,thereby gaining the right to vote.他成了英国公民，因而得到了投票权。

134 yolk   

n.蛋黄，卵黄

参考例句：

• This dish would be more delicious with some yolk powder.加点蛋黄粉，这道菜就会更好吃。
• Egg yolk serves as the emulsifying agent in salad dressing.在色拉调味时，蛋黄能作为乳化剂。

135 destitute   

adj.缺乏的；穷困的

参考例句：

• They were destitute of necessaries of life.他们缺少生活必需品。
• They are destitute of common sense.他们缺乏常识。

136 invertebrates   

n.无脊椎动物( invertebrate的名词复数 )

参考例句：

• Insects and worms are all invertebrates. 昆虫和蠕虫都是无脊椎动物。 来自辞典例句
• In the earthworm and many other invertebrates, these excretory structures are called nephridia. 在蚯蚓和许多其它无脊椎动物中，这些排泄结构称为肾管。 来自辞典例句

137 peripheral   

adj.周边的，外围的

参考例句：

• We dealt with the peripheral aspects of a cost reduction program.我们谈到了降低成本计划的一些外围问题。
• The hotel provides the clerk the service and the peripheral traveling consultation.旅舍提供票务服务和周边旅游咨询。

138 appreciable   

adj.明显的，可见的，可估量的，可觉察的

参考例句：

• There is no appreciable distinction between the twins.在这对孪生子之间看不出有什么明显的差别。
• We bought an appreciable piece of property.我们买下的资产有增值的潜力。

139 olfactory   

adj.嗅觉的

参考例句：

• He is to develop a sensor to substitute for the olfactory abilities of dogs.克罗克将研制一种传感器用以代替狗的嗅觉功能。
• Based on these findings, Keller suspects that each person has an olfactory blind spot.根据这些发现，凯勒推断，每个人都有一个嗅觉盲区。

140 figs   

figures 数字，图形，外形

参考例句：

• The effect of ring dyeing is shown in Figs 10 and 11. 环形染色的影响如图10和图11所示。
• The results in Figs. 4 and 5 show the excellent agreement between simulation and experiment. 图4和图5的结果都表明模拟和实验是相当吻合的。

141 accurately   

adv.准确地，精确地

参考例句：

• It is hard to hit the ball accurately.准确地击中球很难。
• Now scientists can forecast the weather accurately.现在科学家们能准确地预报天气。

142 primitive   

adj.原始的；简单的；n.原(始)人，原始事物

参考例句：

• It is a primitive instinct to flee a place of danger.逃离危险的地方是一种原始本能。
• His book describes the march of the civilization of a primitive society.他的著作描述了一个原始社会的开化过程。

143 investigations   

（正式的）调查( investigation的名词复数 )； 侦查； 科学研究； 学术研究

参考例句：

• His investigations were intensive and thorough but revealed nothing. 他进行了深入彻底的调查，但没有发现什么。
• He often sent them out to make investigations. 他常常派他们出去作调查。

144 streak   

n.条理，斑纹，倾向，少许，痕迹；v.加条纹，变成条纹，奔驰，快速移动

参考例句：

• The Indians used to streak their faces with paint.印第安人过去常用颜料在脸上涂条纹。
• Why did you streak the tree?你为什么在树上刻条纹？

145 disposition   

n.性情，性格；意向，倾向；排列，部署

参考例句：

• He has made a good disposition of his property.他已对财产作了妥善处理。
• He has a cheerful disposition.他性情开朗。

146 streaks   

n.（与周围有所不同的）条纹( streak的名词复数 )；（通常指不好的）特征（倾向）；（不断经历成功或失败的）一段时期v.快速移动( streak的第三人称单数 )；使布满条纹

参考例句：

• streaks of grey in her hair 她头上的绺绺白发
• Bacon has streaks of fat and streaks of lean. 咸肉中有几层肥的和几层瘦的。 来自《现代英汉综合大词典》

147 torpedo   

n.水雷，地雷；v.用鱼雷破坏

参考例句：

• His ship was blown up by a torpedo.他的船被一枚鱼雷炸毁了。
• Torpedo boats played an important role during World War Two.鱼雷艇在第二次世界大战中发挥了重要作用。

148 cylinders   

n.圆筒( cylinder的名词复数 )；圆柱；汽缸；（尤指用作容器的）圆筒状物

参考例句：

• They are working on all cylinders to get the job finished. 他们正在竭尽全力争取把这工作干完。 来自《简明英汉词典》
• That jeep has four cylinders. 那辆吉普车有4个汽缸。 来自《简明英汉词典》

149 fluctuation   

n.(物价的)波动，涨落；周期性变动；脉动

参考例句：

• The erratic fluctuation of market prices are in consequence of unstable economy.经济波动致使市场物价忽起忽落。
• Early and adequate drainage is essential if fluctuation occurs.有波动感时，应及早地充分引流。

150 sparse   

adj.稀疏的，稀稀落落的，薄的

参考例句：

• The teacher's house is in the suburb where the houses are sparse.老师的家在郊区，那里稀稀拉拉有几处房子。
• The sparse vegetation will only feed a small population of animals.稀疏的植物只够喂养少量的动物。

151 meshes   

网孔( mesh的名词复数 )； 网状物； 陷阱； 困境

参考例句：

• The net of Heaven has large meshes, but it lets nothing through. 天网恢恢，疏而不漏。
• This net has half-inch meshes. 这个网有半英寸见方的网孔。

152 specimen   

n.样本，标本

参考例句：

• You'll need tweezers to hold up the specimen.你要用镊子来夹这标本。
• This specimen is richly variegated in colour.这件标本上有很多颜色。

153 formulate   

v.用公式表示；规划；设计；系统地阐述

参考例句：

• He took care to formulate his reply very clearly.他字斟句酌，清楚地做了回答。
• I was impressed by the way he could formulate his ideas.他陈述观点的方式让我印象深刻。

154 distinguished   

adj.卓越的，杰出的，著名的

参考例句：

• Elephants are distinguished from other animals by their long noses.大象以其长长的鼻子显示出与其他动物的不同。
• A banquet was given in honor of the distinguished guests.宴会是为了向贵宾们致敬而举行的。

155 allied   

adj.协约国的；同盟国的

参考例句：

• Britain was allied with the United States many times in history.历史上英国曾多次与美国结盟。
• Allied forces sustained heavy losses in the first few weeks of the campaign.同盟国在最初几周内遭受了巨大的损失。

156 undue   

adj.过分的；不适当的；未到期的

参考例句：

• Don't treat the matter with undue haste.不要过急地处理此事。
• It would be wise not to give undue importance to his criticisms.最好不要过分看重他的批评。

157 nutrient   

adj.营养的，滋养的；n.营养物，营养品

参考例句：

• Magnesium is the nutrient element in plant growth.镁是植物生长的营养要素。
• The roots transmit moisture and nutrient to the trunk and branches.根将水分和养料输送到干和枝。

158 bidder   

n.(拍卖时的)出价人，报价人，投标人

参考例句：

• TV franchises will be auctioned to the highest bidder.电视特许经营权将拍卖给出价最高的投标人。
• The bidder withdrew his bid after submission of his bid.投标者在投标之后撤销了投标书。

159 investigators   

n.调查者，审查者( investigator的名词复数 )

参考例句：

• This memo could be the smoking gun that investigators have been looking for. 这份备忘录可能是调查人员一直在寻找的证据。
• The team consisted of six investigators and two secretaries. 这个团队由六个调查人员和两个秘书组成。 来自《简明英汉词典》

160 volition   

n.意志；决意

参考例句：

• We like to think that everything we do and everything we think is a product of our volition.我们常常认为我们所做和所想的一切都出自自己的意愿。
• Makin said Mr Coombes had gone to the police of his own volition.梅金说库姆斯先生是主动去投案的。

161 dominant   

adj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因

参考例句：

• The British were formerly dominant in India.英国人从前统治印度。
• She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。

162 enumerating   

v.列举，枚举，数( enumerate的现在分词 )

参考例句：

• There is no enumerating the evils of dishonesty here. 欺诈的罪恶在这里难以（无法）一一列举。 来自互联网
• What she used to be most adept at was enumerating. 从前，她最拿手的是数落。 来自互联网

163 deductions   

扣除( deduction的名词复数 )； 结论； 扣除的量； 推演

参考例句：

• Many of the older officers trusted agents sightings more than cryptanalysts'deductions. 许多年纪比较大的军官往往相信特务的发现，而不怎么相信密码分析员的推断。
• You know how you rush at things,jump to conclusions without proper deductions. 你知道你处理问题是多么仓促，毫无合适的演绎就仓促下结论。

164 reigning   

adj.统治的，起支配作用的

参考例句：

• The sky was dark, stars were twinkling high above, night was reigning, and everything was sunk in silken silence. 天很黑，星很繁，夜阑人静。
• Led by Huang Chao, they brought down the reigning house after 300 years' rule. 在黄巢的带领下，他们推翻了统治了三百年的王朝。

165 precipitately   

adv.猛进地

参考例句：

• The number of civil wars continued to rise until about 1990 and then fell precipitately. 而国内战争的数量在1990年以前都有增加，1990年后则锐减。 来自互联网
• His wife and mistress, until an hour ago and inviolate were slipping precipitately from his control. 他的妻子和情妇，直到一小时前还是安安稳稳、不可侵犯的，现在却猛不防正从他的控制下溜走。 来自互联网

166 meditations   

默想( meditation的名词复数 )； 默念； 沉思； 冥想

参考例句：

• Each sentence seems a quarry of rich meditations. 每一句话似乎都给人以许多冥思默想。
• I'm sorry to interrupt your meditations. 我很抱歉，打断你思考问题了。

167 miraculous   

adj.像奇迹一样的，不可思议的

参考例句：

• The wounded man made a miraculous recovery.伤员奇迹般地痊愈了。
• They won a miraculous victory over much stronger enemy.他们战胜了远比自己强大的敌人，赢得了非凡的胜利。

168 savages   

未开化的人，野蛮人( savage的名词复数 )

参考例句：

• There're some savages living in the forest. 森林里居住着一些野人。
• That's an island inhabited by savages. 那是一个野蛮人居住的岛屿。

169 savage   

adj.野蛮的；凶恶的，残暴的；n.未开化的人

参考例句：

• The poor man received a savage beating from the thugs.那可怜的人遭到暴徒的痛打。
• He has a savage temper.他脾气粗暴。

170 virtues   

美德( virtue的名词复数 )； 德行； 优点； 长处

参考例句：

• Doctors often extol the virtues of eating less fat. 医生常常宣扬少吃脂肪的好处。
• She delivered a homily on the virtues of family life. 她进行了一场家庭生活美德方面的说教。

171 metabolic   

adj.新陈代谢的

参考例句：

• Impressive metabolic alternations have been undergone during embryogenesis.在胚胎发生期间经历了深刻的代谢变化。
• A number of intoxicants are associated with metabolic acidosis.许多毒性物质可引起代谢性酸中毒。

172 remarkable   

adj.显著的，异常的，非凡的，值得注意的

参考例句：

• She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
• These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。

173 aptitude   

n.(学习方面的)才能，资质，天资

参考例句：

• That student has an aptitude for mathematics.那个学生有数学方面的天赋。
• As a child,he showed an aptitude for the piano.在孩提时代，他显露出对于钢琴的天赋。

174 pebble   

n.卵石，小圆石

参考例句：

• The bird mistook the pebble for egg and tried to hatch it.这只鸟错把卵石当蛋，想去孵它。
• The pebble made a ripple on the surface of the lake.石子在湖面上激起一个涟漪。

175 victorious   

adj.胜利的，得胜的

参考例句：

• We are certain to be victorious.我们定会胜利。
• The victorious army returned in triumph.获胜的部队凯旋而归。

176 sensational   

adj.使人感动的，非常好的，轰动的，耸人听闻的

参考例句：

• Papers of this kind are full of sensational news reports.这类报纸满是耸人听闻的新闻报道。
• Their performance was sensational.他们的演出妙极了。

177 specify   

vt.指定，详细说明

参考例句：

• We should specify a time and a place for the meeting.我们应指定会议的时间和地点。
• Please specify what you will do.请你详述一下你将做什么。

178 gratuitous   

adj.无偿的，免费的；无缘无故的，不必要的

参考例句：

• His criticism is quite gratuitous.他的批评完全没有根据。
• There's too much crime and gratuitous violence on TV.电视里充斥着犯罪和无端的暴力。

179 mole   

n.胎块；痣；克分子

参考例句：

• She had a tiny mole on her cheek.她的面颊上有一颗小黑痣。
• The young girl felt very self- conscious about the large mole on her chin.那位年轻姑娘对自己下巴上的一颗大痣感到很不自在。

180 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

181 adverse   

adj.不利的；有害的；敌对的，不友好的

参考例句：

• He is adverse to going abroad.他反对出国。
• The improper use of medicine could lead to severe adverse reactions.用药不当会产生严重的不良反应。

182 allude   

v.提及，暗指

参考例句：

• Many passages in Scripture allude to this concept.圣经中有许多经文间接地提到这样的概念。
• She also alluded to her rival's past marital troubles.她还影射了对手过去的婚姻问题。

183 stimulation   

n.刺激，激励，鼓舞

参考例句：

• The playgroup provides plenty of stimulation for the children.幼儿游戏组给孩子很多启发。
• You don't get any intellectual stimulation in this job.你不能从这份工作中获得任何智力启发。

184 retard   

n.阻止，延迟；vt.妨碍，延迟，使减速

参考例句：

• Lack of sunlight will retard the growth of most plants.缺乏阳光会妨碍大多数植物的生长。
• Continuing violence will retard negotiations over the country's future.持续不断的暴力活动会阻碍关系到国家未来的谈判的进行。

185 cellular   

adj.移动的；细胞的，由细胞组成的

参考例句：

• She has a cellular telephone in her car.她的汽车里有一部无线通讯电话机。
• Many people use cellular materials as sensitive elements in hygrometers.很多人用蜂窝状的材料作为测量温度的传感元件。

186 structurally   

在结构上

参考例句：

• The house roof was (structurally) unsound. 这屋顶（结构）不牢固。
• Pinhole on shot-hole damage is never structurally significant. 针孔和蛀洞所造成的危害对结构的影响不大。

187 derive   

v.取得；导出；引申；来自；源自；出自

参考例句：

• We derive our sustenance from the land.我们从土地获取食物。
• We shall derive much benefit from reading good novels.我们将从优秀小说中获得很大好处。

188 complexity   

n.复杂(性)，复杂的事物

参考例句：

• Only now did he understand the full complexity of the problem.直到现在他才明白这一问题的全部复杂性。
• The complexity of the road map puzzled me.错综复杂的公路图把我搞糊涂了。

189 discredit   

vt.使不可置信；n.丧失信义；不信，怀疑

参考例句：

• Their behaviour has bought discredit on English football.他们的行为败坏了英国足球运动的声誉。
• They no longer try to discredit the technology itself.他们不再试图怀疑这种技术本身。

190 immediate   

adj.立即的；直接的，最接近的；紧靠的

参考例句：

• His immediate neighbours felt it their duty to call.他的近邻认为他们有责任去拜访。
• We declared ourselves for the immediate convocation of the meeting.我们主张立即召开这个会议。

191 differentiated   

区分，区别，辨别( differentiate的过去式和过去分词 )； 区别对待； 表明…间的差别，构成…间差别的特征

参考例句：

• The development of mouse kidney tubules requires two kinds of differentiated cells. 小鼠肾小管的发育需要有两种分化的细胞。
• In this enlargement, barley, alfalfa, and sugar beets can be differentiated. 在这张放大的照片上，大麦，苜蓿和甜菜都能被区分开。

192 underlying   

adj.在下面的，含蓄的，潜在的

参考例句：

• The underlying theme of the novel is very serious.小说隐含的主题是十分严肃的。
• This word has its underlying meaning.这个单词有它潜在的含义。

193 conspicuously   

ad.明显地，惹人注目地

参考例句：

• France remained a conspicuously uneasy country. 法国依然是个明显不太平的国家。
• She figured conspicuously in the public debate on the issue. 她在该问题的公开辩论中很引人注目。

194 differentiation   

n.区别，区分

参考例句：

• There can be no differentiation without contrast. 有比较才有差别。
• The operation that is the inverse of differentiation is called integration. 与微分相反的运算叫做积分。

195 purely   

adv.纯粹地，完全地

参考例句：

• I helped him purely and simply out of friendship.我帮他纯粹是出于友情。
• This disproves the theory that children are purely imitative.这证明认为儿童只会单纯地模仿的理论是站不住脚的。

196 irreconcilable   

adj.（指人）难和解的，势不两立的

参考例句：

• These practices are irreconcilable with the law of the Church.这种做法与教规是相悖的。
• These old concepts are irreconcilable with modern life.这些陈旧的观念与现代生活格格不入。

197 prudent   

adj.谨慎的，有远见的，精打细算的

参考例句：

• A prudent traveller never disparages his own country.聪明的旅行者从不贬低自己的国家。
• You must school yourself to be modest and prudent.你要学会谦虚谨慎。

198 specimens   

n.样品( specimen的名词复数 )；范例；（化验的）抽样；某种类型的人

参考例句：

• Astronauts have brought back specimens of rock from the moon. 宇航员从月球带回了岩石标本。
• The traveler brought back some specimens of the rocks from the mountains. 那位旅行者从山上带回了一些岩石标本。 来自《简明英汉词典》

199 deceptive   

adj.骗人的，造成假象的，靠不住的

参考例句：

• His appearance was deceptive.他的外表带有欺骗性。
• The storyline is deceptively simple.故事情节看似简单，其实不然。

200 bristle   

v.（毛发）直立，气势汹汹，发怒；n.硬毛发

参考例句：

• It has a short stumpy tail covered with bristles.它粗短的尾巴上鬃毛浓密。
• He bristled with indignation at the suggestion that he was racist.有人暗示他是个种族主义者，他对此十分恼火。

201 eel   

n.鳗鲡

参考例句：

• He used an eel spear to catch an eel.他用一只捕鳗叉捕鳗鱼。
• In Suzhou,there was a restaurant that specialized in eel noodles.苏州有一家饭馆，他们那里的招牌菜是鳗鱼面。

202 cod   

n.鳕鱼；v.愚弄；哄骗

参考例句：

• They salt down cod for winter use.他们腌鳕鱼留着冬天吃。
• Cod are found in the North Atlantic and the North Sea.北大西洋和北海有鳕鱼。

203 deficient   

adj.不足的，不充份的，有缺陷的

参考例句：

• The crops are suffering from deficient rain.庄稼因雨量不足而遭受损害。
• I always have been deficient in selfconfidence and decision.我向来缺乏自信和果断。

204 colossal   

adj.异常的，庞大的

参考例句：

• There has been a colossal waste of public money.一直存在巨大的公款浪费。
• Some of the tall buildings in that city are colossal.那座城市里的一些高层建筑很庞大。

205 supreme   

adj.极度的，最重要的；至高的，最高的

参考例句：

• It was the supreme moment in his life.那是他一生中最重要的时刻。
• He handed up the indictment to the supreme court.他把起诉书送交最高法院。

206 systematic   

adj.有系统的，有计划的，有方法的

参考例句：

• The way he works isn't very systematic.他的工作不是很有条理。
• The teacher made a systematic work of teaching.这个教师进行系统的教学工作。

207 tadpoles   

n.蝌蚪( tadpole的名词复数 )

参考例句：

• The pond teemed with tadpoles. 池子里有很多蝌蚪。 来自《简明英汉词典》
• Both fish and tadpoles have gills. 鱼和蝌蚪都有鳃。 来自《现代汉英综合大词典》

208 derived   

vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取

参考例句：

• Many English words are derived from Latin and Greek. 英语很多词源出于拉丁文和希腊文。 来自《简明英汉词典》
• He derived his enthusiasm for literature from his father. 他对文学的爱好是受他父亲的影响。 来自《简明英汉词典》

209 cerebral   

adj.脑的，大脑的；有智力的，理智型的

参考例句：

• Your left cerebral hemisphere controls the right-hand side of your body.你的左半脑控制身体的右半身。
• He is a precise,methodical,cerebral man who carefully chooses his words.他是一个一丝不苟、有条理和理智的人，措辞谨慎。

210 spherical   

adj.球形的；球面的

参考例句：

• The Earth is a nearly spherical planet.地球是一个近似球体的行星。
• Many engineers shy away from spherical projection methods.许多工程师对球面投影法有畏难情绪。

211 filament   

n.细丝；长丝；灯丝

参考例句：

• The source of electrons in an electron microscope is a heated filament.电子显微镜中的电子源，是一加热的灯丝。
• The lack of air in the bulb prevents the filament from burning up.灯泡内缺乏空气就使灯丝不致烧掉。

212 lair   

n.野兽的巢穴；躲藏处

参考例句：

• How can you catch tiger cubs without entering the tiger's lair?不入虎穴，焉得虎子？
• I retired to my lair,and wrote some letters.我回到自己的躲藏处，写了几封信。

213 regenerated   

v.新生，再生( regenerate的过去式和过去分词 )

参考例句：

• They are regarded as being enveloped in regenerated gneisses. 它们被认为包围在再生的片麻岩之中。 来自辞典例句
• The party soon regenerated under her leadership. 该党在她的领导下很快焕然一新。 来自辞典例句

214 lapse   

n.过失，流逝，失效，抛弃信仰，间隔；vi.堕落，停止，失效，流逝；vt.使失效

参考例句：

• The incident was being seen as a serious security lapse.这一事故被看作是一次严重的安全疏忽。
• I had a lapse of memory.我记错了。

215 agglomerations   

n.成团，结块（agglomeration的复数形式）

参考例句：

• Shandong Peninsula Agglomerations are the most developed region of Shandong Province. 山东半岛城市群是山东省经济最发达的地区。 来自互联网
• Homogeneous mixing and moistening without the formation of agglomerations or wet spots. 均一的混合和湿度，没有球团或者滴水斑点的产生。 来自互联网

216 polygonal   

adj.多角形的，多边形的

参考例句：

• The grains take on simple polygonal. 颗粒呈简单的多角形。 来自辞典例句
• Use the necessary instrument Polygonal Lasso Tool to outline the mask contour. 使用多边形套索工具将面膜部分选中。 来自互联网

217 elongate   

v.拉长，伸长，延长

参考例句：

• We plan to elongate the cooperation with that company in Australia.我们打算延长与澳洲那家公司的合作关系。
• Corn is treated when the stalk starts to elongate.在玉米秆开始拔节时，给玉米打药。

218 transformation   

n.变化；改造；转变

参考例句：

• Going to college brought about a dramatic transformation in her outlook.上大学使她的观念发生了巨大的变化。
• He was struggling to make the transformation from single man to responsible husband.他正在努力使自己由单身汉变为可靠的丈夫。

219 consolidation   

n.合并,巩固

参考例句：

• The denser population necessitates closer consolidation both for internal and external action. 住得日益稠密的居民，对内和对外都不得不更紧密地团结起来。 来自英汉非文学 - 家庭、私有制和国家的起源
• The state ensures the consolidation and growth of the state economy. 国家保障国营经济的巩固和发展。 来自汉英非文学 - 中国宪法

220 disappearance   

n.消失，消散，失踪

参考例句：

• He was hard put to it to explain her disappearance.他难以说明她为什么不见了。
• Her disappearance gave rise to the wildest rumours.她失踪一事引起了各种流言蜚语。

221 memoir   

n.[pl.]回忆录，自传；记事录

参考例句：

• He has just published a memoir in honour of his captain.他刚刚出了一本传记来纪念他的队长。
• In her memoir,the actress wrote about the bittersweet memories of her first love.在那个女演员的自传中，她写到了自己苦乐掺半的初恋。

222 modification   

n.修改，改进，缓和，减轻

参考例句：

• The law,in its present form,is unjust;it needs modification.现行的法律是不公正的，它需要修改。
• The design requires considerable modification.这个设计需要作大的修改。

223 alimentary   

adj.饮食的，营养的

参考例句：

• He had the disease of alimentary canal.他患了消化道疾病。
• This system is mainly a long tube,called the alimentary canal.这一系统主要是一根长管，称作消化道。

224 plasma   

n.血浆，细胞质，乳清

参考例句：

• Keep some blood plasma back for the serious cases.留一些血浆给重病号。
• The plasma is the liquid portion of blood that is free of cells .血浆是血液的液体部分，不包含各种细胞。

225 membrane   

n.薄膜，膜皮，羊皮纸

参考例句：

• A vibrating membrane in the ear helps to convey sounds to the brain.耳膜的振动帮助声音传送到大脑。
• A plastic membrane serves as selective diffusion barrier.一层塑料薄膜起着选择性渗透屏障的作用。

226 relinquished   

交出，让给( relinquish的过去式和过去分词 )； 放弃

参考例句：

• She has relinquished the post to her cousin, Sir Edward. 她把职位让给了表弟爱德华爵士。
• The small dog relinquished his bone to the big dog. 小狗把它的骨头让给那只大狗。

227 conclusive   

adj.最后的，结论的；确凿的，消除怀疑的

参考例句：

• They produced some fairly conclusive evidence.他们提供了一些相当确凿的证据。
• Franklin did not believe that the French tests were conclusive.富兰克林不相信这个法国人的实验是结论性的。

228 winding   

n.绕，缠，绕组，线圈

参考例句：

• A winding lane led down towards the river.一条弯弯曲曲的小路通向河边。
• The winding trail caused us to lose our orientation.迂回曲折的小道使我们迷失了方向。

229 forth   

adv.向前；向外，往外

参考例句：

• The wind moved the trees gently back and forth.风吹得树轻轻地来回摇晃。
• He gave forth a series of works in rapid succession.他很快连续发表了一系列的作品。

230 laterally   

ad.横向地；侧面地；旁边地

参考例句：

• Shafts were sunk, with tunnels dug laterally. 竖井已经打下，并且挖有横向矿道。
• When the plate becomes unstable, it buckles laterally. 当板失去稳定时，就发生横向屈曲。

231 soldered   

v.（使）焊接，焊合( solder的过去式和过去分词 )

参考例句：

• Three lead wires are soldered to the anchor terminals. 在固定接线端子上焊有三根导线。 来自辞典例句
• He soldered the broken wires together. 他将断了的电线焊接起来。 来自辞典例句

232 twigs   

细枝，嫩枝( twig的名词复数 )

参考例句：

• Some birds build nests of twigs. 一些鸟用树枝筑巢。
• Willow twigs are pliable. 柳条很软。

233 degenerate   

v.退步，堕落；adj.退步的，堕落的；n.堕落者

参考例句：

• He didn't let riches and luxury make him degenerate.他不因财富和奢华而自甘堕落。
• Will too much freedom make them degenerate?太多的自由会令他们堕落吗？

234 degenerated   

衰退，堕落，退化( degenerate的过去式和过去分词 )

参考例句：

• The march degenerated into a riot. 示威游行变成了暴动。
• The wide paved road degenerated into a narrow bumpy track. 铺好的宽阔道路渐渐变窄，成了一条崎岖不平的小径。

235 severed   

v.切断，断绝( sever的过去式和过去分词 )；断，裂

参考例句：

• The doctor said I'd severed a vessel in my leg. 医生说我割断了腿上的一根血管。 来自《简明英汉词典》
• We have severed diplomatic relations with that country. 我们与那个国家断绝了外交关系。 来自《简明英汉词典》

236 lingual   

adj.语言的；舌的

参考例句：

• Over here,they're not even lingual.在这，他们甚至什么话都说不来。
• Its brilliant elegant lingual art can be called"Great works".它那璀灿优美的语言艺术，真可谓“天地妙文”。

237 grafting   

嫁接法，移植法

参考例句：

• Even grafting new blood vessels in place of the diseased coronary arteries has been tried. 甚至移植新血管代替不健康的冠状动脉的方法都已经试过。
• Burns can often be cured by grafting on skin from another part of the same body. 烧伤常常可以用移植身体其它部位的皮肤来治愈。

238 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。

239 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

240 steadily   

adv.稳定地；不变地；持续地

参考例句：

• The scope of man's use of natural resources will steadily grow.人类利用自然资源的广度将日益扩大。
• Our educational reform was steadily led onto the correct path.我们的教学改革慢慢上轨道了。

241 traction   

n.牵引；附着摩擦力

参考例句：

• I'll show you how the traction is applied.我会让你看如何做这种牵引。
• She's injured her back and is in traction for a month.她背部受伤，正在作一个月的牵引治疗。

242 besetting   

adj.不断攻击的v.困扰( beset的现在分词 )；不断围攻；镶；嵌

参考例句：

• Laziness is my besetting sin. 懒惰是我积重难返的恶习。 来自辞典例句
• His besetting sin is laziness. 他所易犯的毛病就是懒惰。 来自辞典例句

243 synthetical   

adj.综合的，合成的

参考例句：

• Studying the value of science is a new and synthetical study. 科学价值的向度研究是一个崭新的综合性跨学科领域研究。 来自互联网
• Among them, sea-island structure flexibilizer had good synthetical properties. 相比较而言，端环氧基聚氨酯醚海岛结构增韧剂的综合性能较好。 来自互联网

244 glandular   

adj.腺体的

参考例句：

• Terry has been laid low with glandular fever for nearly a month now.特里由于功能性高烧已卧床近一个月了。
• A malignant tumor originating in glandular tissue.腺癌起源于腺性组织的恶性肿瘤。

245 secretion   

n.分泌

参考例句：

• Is there much secretion from your eyes?你眼里的分泌物多吗？
• In addition,excessive secretion of oil,water scarcity are also major factors.除此之外，油脂分泌过盛、缺水也都是主要因素。

246 unravel   

v.弄清楚（秘密）；拆开，解开，松开

参考例句：

• He was good with his hands and could unravel a knot or untangle yarn that others wouldn't even attempt.他的手很灵巧，其他人甚至都不敢尝试的一些难解的绳结或缠在一起的纱线，他都能解开。
• This is the attitude that led him to unravel a mystery that long puzzled Chinese historians.正是这种态度使他解决了长期以来使中国历史学家们大惑不解的谜。

247 contraction   

n.缩略词，缩写式，害病

参考例句：

• The contraction of this muscle raises the lower arm.肌肉的收缩使前臂抬起。
• The forces of expansion are balanced by forces of contraction.扩张力和收缩力相互平衡。

248 upwards   

adv.向上，在更高处...以上

参考例句：

• The trend of prices is still upwards.物价的趋向是仍在上涨。
• The smoke rose straight upwards.烟一直向上升。

249 volitional   

adj.意志的，凭意志的，有意志的

参考例句：

• The image consists in our rational,volitional,affective faculties,and in our bodies.神的形象存在于我们的理性、意志，和情感的能力中，也存在于我们的身体内。
• The endurance of setbacks is a standard mat can evaluate the volitional character of a person.挫折承受能力是衡量人的意志品质的一个重要指标。

250 psychical   

adj.有关特异功能现象的；有关特异功能官能的；灵魂的；心灵的

参考例句：

• Conclusion: The Liuhe-lottery does harm to people, s psychical health and should be for bidden. 结论：“六合彩”赌博有害人们心理卫生，应予以严禁。 来自互联网

251 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。

252 requisite   

adj.需要的，必不可少的；n.必需品

参考例句：

• He hasn't got the requisite qualifications for the job.他不具备这工作所需的资格。
• Food and air are requisite for life.食物和空气是生命的必需品。

253 pulp   

n.果肉，纸浆；v.化成纸浆，除去...果肉，制成纸浆

参考例句：

• The pulp of this watermelon is too spongy.这西瓜瓤儿太肉了。
• The company manufactures pulp and paper products.这个公司制造纸浆和纸产品。

254 condensation   

n.压缩，浓缩；凝结的水珠

参考例句：

• A cloud is a condensation of water vapour in the atmosphere.云是由大气中的水蒸气凝结成的。
• He used his sleeve to wipe the condensation off the glass.他用袖子擦掉玻璃上凝结的水珠。

255 descend   

vt./vi.传下来，下来，下降

参考例句：

• I hope the grace of God would descend on me.我期望上帝的恩惠。
• We're not going to descend to such methods.我们不会沦落到使用这种手段。

256 downwards   

adj./adv.向下的（地），下行的（地）

参考例句：

• He lay face downwards on his bed.他脸向下伏在床上。
• As the river flows downwards,it widens.这条河愈到下游愈宽。

257 physiology   

n.生理学，生理机能

参考例句：

• He bought a book about physiology.他买了一本生理学方面的书。
• He was awarded the Nobel Prize for achievements in physiology.他因生理学方面的建树而被授予诺贝尔奖。

258 expounded   

论述，详细讲解( expound的过去式和过去分词 )

参考例句：

• He expounded his views on the subject to me at great length. 他详细地向我阐述了他在这个问题上的观点。
• He warmed up as he expounded his views. 他在阐明自己的意见时激动起来了。

259 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

260 indirectly   

adv.间接地，不直接了当地

参考例句：

• I heard the news indirectly.这消息我是间接听来的。
• They were approached indirectly through an intermediary.通过一位中间人，他们进行了间接接触。

261 supremacy   

n.至上；至高权力

参考例句：

• No one could challenge her supremacy in gymnastics.她是最优秀的体操运动员，无人能胜过她。
• Theoretically,she holds supremacy as the head of the state.从理论上说，她作为国家的最高元首拥有至高无上的权力。

262 eminently   

adv.突出地；显著地；不寻常地

参考例句：

• She seems eminently suitable for the job. 她看来非常适合这个工作。
• It was an eminently respectable boarding school. 这是所非常好的寄宿学校。 来自《简明英汉词典》

263 contention   

n.争论，争辩，论战；论点，主张

参考例句：

• The pay increase is the key point of contention. 加薪是争论的焦点。
• The real bone of contention,as you know,is money.你知道，争论的真正焦点是钱的问题。

264 suspense   

n.（对可能发生的事）紧张感，担心，挂虑

参考例句：

• The suspense was unbearable.这样提心吊胆的状况实在叫人受不了。
• The director used ingenious devices to keep the audience in suspense.导演用巧妙手法引起观众的悬念。

265 vibrations   

n.摆动( vibration的名词复数 )；震动；感受；（偏离平衡位置的）一次性往复振动

参考例句：

• We could feel the vibrations from the trucks passing outside. 我们可以感到外面卡车经过时的颤动。
• I am drawn to that girl; I get good vibrations from her. 我被那女孩吸引住了，她使我产生良好的感觉。 来自《简明英汉词典》

266 stimulates   

v.刺激( stimulate的第三人称单数 )；激励；使兴奋；起兴奋作用，起刺激作用，起促进作用

参考例句：

• Exercise stimulates the body. 运动促进身体健康。 来自《简明英汉词典》
• Alcohol stimulates the action of the heart. 酒刺激心脏的活动。 来自《现代英汉综合大词典》

267 cones   

n.（人眼）圆锥细胞；圆锥体( cone的名词复数 )；球果；圆锥形东西；（盛冰淇淋的）锥形蛋卷筒

参考例句：

• In the pines squirrels commonly chew off and drop entire cones. 松树上的松鼠通常咬掉和弄落整个球果。 来自辞典例句
• Many children would rather eat ice cream from cones than from dishes. 许多小孩喜欢吃蛋卷冰淇淋胜过盘装冰淇淋。 来自辞典例句

268 constituents   

n.选民( constituent的名词复数 )；成分；构成部分；要素

参考例句：

• She has the full support of her constituents. 她得到本区选民的全力支持。
• Hydrogen and oxygen are the constituents of water. 氢和氧是水的主要成分。 来自《简明英汉词典》

269 epidermis   

n.表皮

参考例句：

• The external layer of skin is called the epidermis.皮的外层叫表皮。
• There is a neoplasm originating in his leg's epidermis.他的腿上有个生长在表皮上的肿瘤。

270 attained   

（通常经过努力）实现( attain的过去式和过去分词 )； 达到； 获得； 达到（某年龄、水平、状况）

参考例句：

• She has attained the degree of Master of Arts. 她已获得文学硕士学位。
• Lu Hsun attained a high position in the republic of letters. 鲁迅在文坛上获得崇高的地位。

271 specified   

adj.特定的

参考例句：

• The architect specified oak for the wood trim. 那位建筑师指定用橡木做木饰条。
• It is generated by some specified means. 这是由某些未加说明的方法产生的。

272 specifies   

v.指定( specify的第三人称单数 )；详述；提出…的条件；使具有特性

参考例句：

• The third clause of the contract specifies steel sashes for the windows. 合同的第三款指定使用钢窗。 来自《简明英汉词典》
• The contract specifies red tiles, not slates, for the roof. 合同规定屋顶用红瓦，并非石板瓦。 来自《现代汉英综合大词典》

273 plausibility   

n. 似有道理, 能言善辩

参考例句：

• We can add further plausibility to the above argument. 我们可以在上述论据之外，再进一步增添一个合理的论据。
• Let us consider the charges she faces, and the legal plausibility of those charges. 让我们考虑一下她面临的指控以及这些指控在法律上的可信性。

274 incapable   

adj.无能力的，不能做某事的

参考例句：

• He would be incapable of committing such a cruel deed.他不会做出这么残忍的事。
• Computers are incapable of creative thought.计算机不会创造性地思维。

275 precisely   

adv.恰好，正好，精确地，细致地

参考例句：

• It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
• The man adjusted very precisely.那个人调得很准。

276 insulation   

n.隔离；绝缘；隔热

参考例句：

• Please examine the insulation of the electric wires in my house.请检查一下我屋子里电线的绝缘情况。
• It is always difficult to assure good insulation between the electric leads.要保证两个电触头之间有良好的绝缘总是很困难的。

277 cistern   

n.贮水池

参考例句：

• The cistern is empty but soon fills again.蓄水池里现在没水，但不久就会储满水的。
• The lavatory cistern overflowed.厕所水箱的水溢出来了

278 dribble   

v.点滴留下，流口水；n.口水

参考例句：

• Melted wax dribbled down the side of the candle.熔化了的蜡一滴滴从蜡烛边上流下。
• He wiped a dribble of saliva from his chin.他擦掉了下巴上的几滴口水。

279 intelligible   

adj.可理解的，明白易懂的，清楚的

参考例句：

• This report would be intelligible only to an expert in computing.只有计算机运算专家才能看懂这份报告。
• His argument was barely intelligible.他的论点不易理解。

280 cogently   

adv.痛切地，中肯地

参考例句：

• Her case was cogently argued. 她的案件辩驳得很有说服力。 来自辞典例句

281 capillaries   

毛细管，毛细血管( capillary的名词复数 )

参考例句：

• The blood flows from the capillaries back into the veins. 血从毛细血管流回静脉。
• While Joe sleeps, a large percentage of his capillaries are inactive. 当乔睡觉时，他的毛细血管大部分是不工作的。

282 insufficient   

adj.(for，of)不足的，不够的

参考例句：

• There was insufficient evidence to convict him.没有足够证据给他定罪。
• In their day scientific knowledge was insufficient to settle the matter.在他们的时代，科学知识还不能足以解决这些问题。

283 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

284 penetrate   

v.透(渗)入；刺入，刺穿；洞察，了解

参考例句：

• Western ideas penetrate slowly through the East.西方观念逐渐传入东方。
• The sunshine could not penetrate where the trees were thickest.阳光不能透入树木最浓密的地方。

285 doctrines   

n.教条( doctrine的名词复数 )；教义；学说；（政府政策的）正式声明

参考例句：

• To modern eyes, such doctrines appear harsh, even cruel. 从现代的角度看，这样的教义显得苛刻，甚至残酷。 来自《简明英汉词典》
• His doctrines have seduced many into error. 他的学说把许多人诱入歧途。 来自《现代汉英综合大词典》