Since the intimate connexion of the heart with the lungs, which is apparent in the human subject, has been the probable cause of the errors that have been committed on this point, they plainly do amiss who, pretending to speak of the parts of animals generally, as anatomists for the most part do, confine their researches to the human body alone, and that when it is dead. They obviously do not act otherwise than he who, having studied the forms of a single commonwealth2, should set about the composition of a general system of polity; or who, having taken cognizance of the nature of a single field, should imagine that he had mastered the science of agriculture; or who, upon the ground of one particular proposition, should proceed to draw general conclusions.
Had anatomists only been as conversant3 with the dissection4 of the lower animals as they are with that of the human body, the matters that have hitherto kept them in a perplexity of doubt would, in my opinion, have met them freed from every kind of difficulty.
And first, in fishes, in which the heart consists of but a single ventricle, being devoid5 of lungs, the thing is sufficiently6 manifest. Here the sac, which is situated7 at the base of the heart, and is the part analogous8 to the auricle in man, plainly forces the blood into the heart, and the heart, in its turn, conspicuously9 transmits it by a pipe or artery11, or vessel12 analogous to an artery; these are facts which are confirmed by simple ocular inspection13, as well as by a division of the vessel, when the blood is seen to be projected by each pulsation14 of the heart.
The same thing is also not difficult of demonstration15 in those animals that have, as it were, no more than a single ventricle to the heart, such as toads16, frogs, serpents, and lizards17, which have lungs in a certain sense, as they have a voice. I have many observations by me on the admirable structure of the lungs of these animals, and matters appertaining, which, however, I cannot introduce in this place. Their anatomy18 plainly shows us that the blood is transferred in them from the veins19 to the arteries in the same manner as in higher animals, viz., by the action of the heart; the way, in fact, is patent, open, manifest; there is no difficulty, no room for doubt about it; for in them the matter stands precisely21 as it would in man were the septum of his heart perforated or removed, or one ventricle made out of two; and this being the case, I imagine that no one will doubt as to the way by which the blood may pass from the veins into the arteries.
But as there are actually more animals which have no lungs than there are furnished with them, and in like manner a greater number which have only one ventricle than there are with two, it is open to us to conclude, judging from the mass or multitude of living creatures, that for the major part, and generally, there is an open way by which the blood is transmitted from the veins through the sinuses or cavities of the heart into the arteries.
I have, however, cogitating22 with myself, seen further, that the same thing obtained most obviously in the embryos23 of those animals that have lungs; for in the foetus the four vessels25 belonging to the heart, viz., the vena cava, the pulmonary artery, the pulmonary vein20, and the great artery or aorta26, are all connected otherwise than in the adult, a fact sufficiently known to every anatomist. The first contact and union of the vena cava with the pulmonary veins, which occurs before the cava opens properly into the right ventricle of the heart, or gives off the coronary vein, a little above its escape from the liver, is by a lateral27 anastomosis; this is an ample foramen, of an oval form, communicating between the cava and the pulmonary vein, so that the blood is free to flow in the greatest abundance by that foramen from the vena cava into the pulmonary vein, and left auricle, and from thence into the left ventricle. Further, in this foramen ovale, from that part which regards the pulmonary vein, there is a thin tough membrane28, larger than the opening, extended like an operculum or cover; this membrane in the adult blocking up the foramen, and adhering on all sides, finally closes it up, and almost obliterates29 every trace of it. In the foetus, however, this membrane is so contrived30 that falling loosely upon itself, it permits a ready access to the lungs and heart, yielding a passage to the blood which is streaming from the cava, and hindering the tide at the same time from flowing back into that vein. All things, in short, permit us to believe that in the embryo24 the blood must constantly pass by this foramen from the vena cava into the pulmonary vein, and from thence into the left auricle of the heart; and having once entered there, it can never regurgitate.
Another union is that by the pulmonary artery, and is effected when that vessel divides into two branches after its escape from the right ventricle of the heart. It is as if to the two trunks already mentioned a third were superadded, a kind of arterial canal, carried obliquely31 from the pulmonary artery, to perforate and terminate in the great artery or aorta. So that in the dissection of the embryo, as it were, two aortas32, or two roots of the great artery, appear springing from the heart. This canal shrinks gradually after birth, and after a time becomes withered33, and finally almost removed, like the umbilical vessels.
The arterial canal contains no membrane or valve to direct or impede34 the flow of blood in this or in that direction: for at the root of the pulmonary artery, of which the arterial canal is the continuation in the foetus, there are three semilunar valves, which open from within outwards35, and oppose no obstacle to the blood flowing in this direction or from the right ventricle into the pulmonary artery and aorta; but they prevent all regurgitation from the aorta or pulmonic vessels back upon the right ventricle; closing with perfect accuracy, they oppose an effectual obstacle to everything of the kind in the embryo. So that there is also reason to believe that when the heart contracts, the blood is regularly propelled by the canal or passage indicated from the right ventricle into the aorta.
What is commonly said in regard to these two great communications, to wit, that they exist for the nutrition of the lungs, is both improbable and inconsistent; seeing that in the adult they are closed up, abolished, and consolidated36, although the lungs, by reason of their heat and motion, must then be presumed to require a larger supply of nourishment37. The same may be said in regard to the assertion that the heart in the embryo does not pulsate38, that it neither acts nor moves, so that nature was forced to make these communications for the nutrition of the lungs. This is plainly false; for simple inspection of the incubated egg, and of embryos just taken out of the uterus, shows that the heart moves in them precisely as in adults, and that nature feels no such necessity. I have myself repeatedly seen these motions, and Aristotle is likewise witness of their reality. “The pulse,” he observes, “inheres in the very constitution of the heart, and appears from the beginning as is learned both from the dissection of living animals and the formation of the chick in the egg.”8 But we further observe that the passages in question are not only pervious up to the period of birth in man, as well as in other animals, as anatomists in general have described them, but for several months subsequently, in some indeed for several years, not to say for the whole course of life; as, for example, in the goose, snipe, and various birds and many of the smaller animals. And this circumstance it was, perhaps, that imposed upon Botallus, who thought he had discovered a new passage for the blood from the vena cava into the left ventricle of the heart; and I own that when I met with the same arrangement in one of the larger members of the mouse family, in the adult state, I was myself at first led to something of a like conclusion.
From this it will be understood that in the human embryo, and in the embryos of animals in which the communications are not closed, the same thing happens, namely, that the heart by its motion propels the blood by obvious and open passages from the vena cava into the aorta through the cavities of both the ventricles, the right one receiving the blood from the auricle, and propelling it by the pulmonary artery and its continuation, named the ductus arteriosus, into the aorta; the left, in like manner, charged by the contraction39 of its auricle, which has received its supply through the foramen ovale from the vena cava, contracting, and projecting the blood through the root of the aorta into the trunk of that vessel.
In embryos, consequently, whilst the lungs are yet in a state of inaction, performing no function, subject to no motion any more than if they had not been present, nature uses the two ventricles of the heart as if they formed but one, for the transmission of the blood. The condition of the embryos of those animals which have lungs, whilst these organs are yet in abeyance40 and not employed, is the same as that of those animals which have no lungs.
So it clearly appears in the case of the foetus that the heart by its action transfers the blood from the vena cava into the aorta, and that by a route as obvious and open, as if in the adult the two ventricles were made to communicate by the removal of their septum. We therefore find that in the greater number of animals — in all, indeed, at a certain period of their existence — the channels for the transmission of the blood through the heart are conspicuous10. But we have to inquire why in some creatures — those, namely, that have warm blood, and that have attained41 to the adult age, man among the number — we should not conclude that the same thing is accomplished42 through the substance of the lungs, which in the embryo, and at a time when the function of these organs is in abeyance, nature effects by the direct passages described, and which, indeed, she seems compelled to adopt through want of a passage by the lungs; or why it should be better (for nature always does that which is best) that she should close up the various open routes which she had formerly43 made use of in the embryo and foetus, and still uses in all other animals. Not only does she thereby44 open up no new apparent channels for the passages of the blood, but she even shuts up those which formerly existed.
And now the discussion is brought to this point, that they who inquire into the ways by which the blood reaches the left ventricle of the heart: and pulmonary veins from the vena cava, will pursue the wisest course if they seek by dissection to discover the causes why in the larger and more perfect animals of mature age nature has rather chosen to make the blood percolate45 the parenchyma of the lungs, than, as in other instances, chosen a direct and obvious course — for I assume that no other path or mode of transit46 can be entertained. It must be because the larger and more perfect animals are warmer, and when adult their heat greater — ignited, as I might say, and requiring to be damped or mitigated47, that the blood is sent through the lungs, in order that it may be tempered by the air that is inspired, and prevented from boiling up, and so becoming extinguished, or something else of the sort. But to determine these matters, and explain them satisfactorily, were to enter on a speculation48 in regard to the office of the lungs and the ends for which they exist. Upon such a subject, as well as upon what pertains49 to respiration50, to the necessity and use of the air, etc., as also to the variety and diversity of organs that exist in the bodies of animals in connexion with these matters, although I have made a vast number of observations, I shall not speak till I can more conveniently set them forth51 in a treatise52 apart, lest I should be held as wandering too wide of my present purpose, which is the use and motion of the heart, and be charged with speaking of things beside the question, and rather complicating53 and quitting than illustrating54 it. And now returning to my immediate55 subject, I go on with what yet remains56 for demonstration, viz., that in the more perfect and warmer adult animals, and man, the blood passes from the right ventricle of the heart by the pulmonary artery, into the lungs, and thence by the pulmonary veins into the left auricle, and from there into the left ventricle of the heart. And, first, I shall show that this may be so, and then I shall prove that it is so in fact.
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1
arteries
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| n.动脉( artery的名词复数 )；干线，要道 | |
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commonwealth
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| n.共和国，联邦，共同体 | |
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conversant
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| adj.亲近的，有交情的，熟悉的 | |
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dissection
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| n.分析；解剖 | |
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devoid
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| adj.全无的，缺乏的 | |
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sufficiently
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| adv.足够地，充分地 | |
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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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analogous
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| adj.相似的；类似的 | |
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conspicuously
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| ad.明显地，惹人注目地 | |
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conspicuous
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| adj.明眼的，惹人注目的；炫耀的，摆阔气的 | |
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11
artery
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| n.干线，要道；动脉 | |
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12
vessel
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| n.船舶；容器，器皿；管，导管，血管 | |
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13
inspection
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| n.检查，审查，检阅 | |
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pulsation
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| n.脉搏，悸动，脉动；搏动性 | |
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15
demonstration
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| n.表明，示范，论证，示威 | |
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16
toads
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| n.蟾蜍，癞蛤蟆( toad的名词复数 ) | |
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17
lizards
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| n.蜥蜴( lizard的名词复数 ) | |
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anatomy
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| n.解剖学，解剖；功能，结构，组织 | |
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19
veins
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| n.纹理；矿脉( vein的名词复数 )；静脉；叶脉；纹理 | |
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vein
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| n.血管，静脉；叶脉，纹理；情绪；vt.使成脉络 | |
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21
precisely
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| adv.恰好，正好，精确地，细致地 | |
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cogitating
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| v.认真思考，深思熟虑( cogitate的现在分词 ) | |
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23
embryos
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| n.晶胚；胚，胚胎( embryo的名词复数 ) | |
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embryo
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| n.胚胎，萌芽的事物 | |
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25
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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26
aorta
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| n.主动脉 | |
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lateral
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| adj.侧面的，旁边的 | |
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membrane
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| n.薄膜，膜皮，羊皮纸 | |
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29
obliterates
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| v.除去( obliterate的第三人称单数 )；涂去；擦掉；彻底破坏或毁灭 | |
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30
contrived
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| adj.不自然的，做作的；虚构的 | |
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31
obliquely
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| adv.斜； 倾斜； 间接； 不光明正大 | |
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aortas
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| n.主动脉；主动脉( aorta的名词复数 ) | |
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33
withered
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| adj. 枯萎的，干瘪的，（人身体的部分器官）因病萎缩的或未发育良好的 动词wither的过去式和过去分词形式 | |
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34
impede
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| v.妨碍，阻碍，阻止 | |
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outwards
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| adj.外面的，公开的，向外的；adv.向外；n.外形 | |
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consolidated
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| a.联合的 | |
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nourishment
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| n.食物，营养品；营养情况 | |
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38
pulsate
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| v.有规律的跳动 | |
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39
contraction
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| n.缩略词，缩写式，害病 | |
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40
abeyance
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| n.搁置，缓办，中止，产权未定 | |
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41
attained
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| （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） | |
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42
accomplished
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| adj.有才艺的；有造诣的；达到了的 | |
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43
formerly
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| adv.从前，以前 | |
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44
thereby
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| adv.因此，从而 | |
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45
percolate
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| v.过滤，渗透 | |
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46
transit
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| n.经过，运输；vt.穿越，旋转；vi.越过 | |
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47
mitigated
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| v.减轻，缓和( mitigate的过去式和过去分词 ) | |
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48
speculation
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| n.思索，沉思；猜测；投机 | |
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49
pertains
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| 关于( pertain的第三人称单数 )； 有关； 存在； 适用 | |
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50
respiration
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| n.呼吸作用；一次呼吸；植物光合作用 | |
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51
forth
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| adv.向前；向外，往外 | |
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52
treatise
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| n.专著；(专题)论文 | |
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53
complicating
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| 使复杂化( complicate的现在分词 ) | |
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54
illustrating
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| 给…加插图( illustrate的现在分词 )； 说明； 表明； （用示例、图画等）说明 | |
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55
immediate
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| adj.立即的；直接的，最接近的；紧靠的 | |
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56
remains
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| n.剩余物，残留物；遗体，遗迹 | |
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