Now there are three degrees of composition; and of these the first in order, as all will allow, is composition out of what some call the elements, such as earth, air, water, fire. Perhaps, however, it would be more accurate to say composition out of the elementary forces; nor indeed out of all of these, but out of a limited number of them, as defined in previous treatises3. For fluid and solid, hot and cold, form the material of all composite bodies; and all other differences are secondary to these, such differences, that is, as heaviness or lightness, density5 or rarity, roughness or smoothness, and any other such properties of matter as there may be, second degree of composition is that by which the homogeneous parts of animals, such as bone, flesh, and the like, are constituted out of the primary substances. The third and last stage is the composition which forms the heterogeneous6 parts, such as face, hand, and the rest.
Now the order of actual development and the order of logical existence are always the inverse7 of each other. For that which is posterior in the order of development is antecedent in the order of nature, and that is genetically8 last which in nature is first.
(That this is so is manifest by induction9; for a house does not exist for the sake of bricks and stones, but these materials for the sake of the house; and the same is the case with the materials of other bodies. Nor is induction required to show this; it is included in our conception of generation. For generation is a process from a something to a something; that which is generated having a cause in which it originates and a cause in which it ends. The originating cause is the primary efficient cause, which is something already endowed with tangible10 existence, while the final cause is some definite form or similar end; for man generates man, and plant generates plant, in each case out of the underlying11 material.)
In order of time, then, the material and the generative process must necessarily be anterior12 to the being that is generated; but in logical order the definitive13 character and form of each being precedes the material. This is evident if one only tries to define the process of formation. For the definition of house-building includes and presupposes that of the house; but the definition of the house does not include nor presuppose that of house-building; and the same is true of all other productions. So that it must necessarily be that the elementary material exists for the sake of the homogeneous parts, seeing that these are genetically posterior to it, just as the heterogeneous parts are posterior genetically to them. For these heterogeneous parts have reached the end and goal, having the third degree of composition, in which degree generation or development often attains14 its final term.
Animals, then, are composed of homogeneous parts, and are also composed of heterogeneous parts. The former, however, exist for the sake of the latter. For the active functions and operations of the body are carried on by these; that is, by the heterogeneous parts, such as the eye, the nostril15, the whole face, the fingers, the hand, and the whole arm. But inasmuch as there is a great variety in the functions and motions not only of aggregate16 animals but also of the individual organs, it is necessary that the substances out of which these are composed shall present a diversity of properties. For some purposes softness is advantageous17, for others hardness; some parts must be capable of extension, others of flexion. Such properties, then, are distributed separately to the different homogeneous parts, one being soft another hard, one fluid another solid, one viscous18 another brittle19; whereas each of the heterogeneous parts presents a combination of multifarious properties. For the hand, to take an example, requires one property to enable it to effect pressure, and another and different property for simple prehension. For this reason the active or executive parts of the body are compounded out of bones, sinews, flesh, and the like, but not these latter out of the former.
So far, then, as has yet been stated, the relations between these two orders of parts are determined by a final cause. We have, however, to inquire whether necessity may not also have a share in the matter; and it must be admitted that these mutual20 relations could not from the very beginning have possibly been other than they are. For heterogeneous parts can be made up out of homogeneous parts, either from a plurality of them, or from a single one, as is the case with some of the viscera which, varying in configuration21, are yet, to speak broadly, formed from a single homogeneous substance; but that homogeneous substances should be formed out of a combination of heterogeneous parts is clearly an impossibility. For these causes, then, some parts of animals are simple and homogeneous, while others are composite and heterogeneous; and dividing the parts into the active or executive and the sensitive, each one of the former is, as before said, heterogeneous, and each one of the latter homogeneous. For it is in homogeneous parts alone that sensation can occur, as the following considerations show.
Each sense is confined to a single order of sensibles, and its organ must be such as to admit the action of that kind or order. But it is only that which is endowed with a property in posse that is acted on by that which has the like property in esse, so that the two are the same in kind, and if the latter is single so also is the former. Thus it is that while no physiologists22 ever dream of saying of the hand or face or other such part that one is earth, another water, another fire, they couple each separate sense-organ with a separate element, asserting this one to be air and that other to be fire.
Sensation, then, is confined to the simple or homogeneous parts. But, as might reasonably be expected, the organ of touch, though still homogeneous, is yet the least simple of all the sense-organs. For touch more than any other sense appears to be correlated to several distinct kinds of objects, and to recognize more than one category of contrasts, heat and cold, for instance, solidity and fluidity, and other similar oppositions23. Accordingly, the organ which deals with these varied24 objects is of all the sense-organs the most corporeal25, being either the flesh, or the substance which in some animals takes the place of flesh.
Now as there cannot possibly be an animal without sensation, it follows as a necessary consequence that every animal must have some homogeneous parts; for these alone are capable of sensation, the heterogeneous parts serving for the active functions. Again, as the sensory26 faculty27, the motor faculty, and the nutritive faculty are all lodged28 in one and the same part of the body, as was stated in a former treatise4, it is necessary that the part which is the primary seat of these principles shall on the one hand, in its character of general sensory recipient29, be one of the simple parts; and on the other hand shall, in its motor and active character, be one of the heterogeneous parts. For this reason it is the heart which in sanguineous animals constitutes this central part, and in bloodless animals it is that which takes the place of a heart. For the heart, like the other viscera, is one of the homogeneous parts; for, if cut up, its pieces are homogeneous in substance with each other. But it is at the same time heterogeneous in virtue30 of its definite configuration. And the same is true of the other so-called viscera, which are indeed formed from the same material as the heart. For all these viscera have a sanguineous character owing to their being situated31 upon vascular32 ducts and branches. For just as a stream of water deposits mud, so the various viscera, the heart excepted, are, as it were, deposits from the stream of blood in the vessels33. And as to the heart, the very starting-point of the vessels, and the actual seat of the force by which the blood is first fabricated, it is but what one would naturally expect, that out of the selfsame nutriment of which it is the recipient its own proper substance shall be formed. Such, then, are the reasons why the viscera are of sanguineous aspect; and why in one point of view they are homogeneous, in another heterogeneous.
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1
forth
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| adv.向前；向外，往外 | |
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determined
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| adj.坚定的；有决心的 | |
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treatises
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| n.专题著作，专题论文，专著( treatise的名词复数 ) | |
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treatise
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| n.专著；(专题)论文 | |
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density
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| n.密集，密度，浓度 | |
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heterogeneous
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| adj.庞杂的；异类的 | |
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inverse
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| adj.相反的，倒转的，反转的；n.相反之物；v.倒转 | |
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genetically
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| adv.遗传上 | |
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induction
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| n.感应，感应现象 | |
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tangible
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| adj.有形的，可触摸的，确凿的，实际的 | |
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underlying
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| adj.在下面的，含蓄的，潜在的 | |
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anterior
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| adj.较早的；在前的 | |
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definitive
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| adj.确切的，权威性的；最后的，决定性的 | |
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attains
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| （通常经过努力）实现( attain的第三人称单数 )； 达到； 获得； 达到（某年龄、水平、状况） | |
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nostril
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| n.鼻孔 | |
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aggregate
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| adj.总计的，集合的；n.总数；v.合计；集合 | |
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advantageous
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| adj.有利的；有帮助的 | |
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viscous
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| adj.粘滞的，粘性的 | |
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brittle
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| adj.易碎的；脆弱的；冷淡的；(声音)尖利的 | |
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mutual
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| adj.相互的，彼此的；共同的，共有的 | |
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configuration
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| n.结构，布局，形态，(计算机)配置 | |
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physiologists
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| n.生理学者( physiologist的名词复数 )；生理学( physiology的名词复数 )；生理机能 | |
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oppositions
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| （强烈的）反对( opposition的名词复数 )； 反对党； （事业、竞赛、游戏等的）对手； 对比 | |
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varied
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| adj.多样的，多变化的 | |
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corporeal
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| adj.肉体的，身体的；物质的 | |
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sensory
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| adj.知觉的，感觉的，知觉器官的 | |
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faculty
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| n.才能；学院，系；(学院或系的)全体教学人员 | |
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lodged
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| v.存放( lodge的过去式和过去分词 )；暂住；埋入；（权利、权威等）归属 | |
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recipient
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| a.接受的,感受性强的 n.接受者,感受者,容器 | |
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virtue
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| n.德行，美德；贞操；优点；功效，效力 | |
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situated
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| adj.坐落在...的，处于某种境地的 | |
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vascular
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| adj.血管的，脉管的 | |
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vessels
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| 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 | |
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