That this is possible, and that there is nothing to prevent it from being so, appears when we reflect on the way in which water permeating2 the earth produces springs and rivulets3, or when we speculate on the means by which the sweat passes through the skin, or the urine through the substance of the kidneys. It is well known that persons who use the Spa waters or those of La Madonna, in the territories of Padua, or others of an acidulous4 or vitriolated nature, or who simply swallow drinks by the gallon, pass all off again within an hour or two by the bladder. Such a quantity of liquid must take some short time in the concoction5: it must pass through the liver (it is allowed by all that the juices of the food we consume pass twice through this organ in the course of the day); it must flow through the veins, through the tissues of the kidneys, and through the ureters into the bladder.
To those, therefore, whom I hear denying that the blood, aye, the whole mass of the blood, may pass through the substance of the lungs, even as the nutritive juices percolate6 the liver, asserting such a proposition to be impossible, and by no means to be entertained as credible7, I reply, with the poet, that they are of that race of men who, when they will, assent8 full readily, and when they will not, by no manner of means; who, when their assent is wanted, fear, and when it is not, fear not to give it.
The substance of the liver is extremely dense9, so is that of the kidney; the lungs, however, are of a much looser texture10, and if compared with the kidneys are absolutely spongy. In the liver there is no forcing, no impelling11 power; in the lungs the blood is forced on by the pulse of the right ventricle, the necessary effect of whose impulse is the distension12 of the vessels13 and the pores of the lungs. And then the lungs, in respiration15, are perpetually rising and falling: motions, the effect of which must needs be to open and shut the pores and vessels, precisely16 as in the case of a sponge, and of parts having a spongy structure, when they are alternately compressed and again are suffered to expand. The liver, on the contrary, remains17 at rest, and is never seen to be dilated18 or constricted19. Lastly, if no one denies the possibility in man, oxen, and the larger animals generally, of the whole of the ingested juices passing through the liver, in order to reach the vena cava, for this reason, that if nourishment20 is to go on, these juices must needs get into the veins, and there is no other way but the one indicated, why should not the same arguments be held of avail for the passage of the blood in adults through the lungs? Why not maintain, with Columbus, that skilful21 and learned anatomist, that it must be so from the capacity and structure of the pulmonary vessels, and from the fact of the pulmonary veins and ventricle corresponding with them, being always found to contain blood, which must needs have come from the veins, and by no other passage save through the lungs? Columbus, and we also, from what precedes, from dissections, and other arguments, conceive the thing to be clear. But as there are some who admit nothing unless upon authority, let them learn that the truth I am contending for can be confirmed from Galen’s own words, namely, that not only may the blood be transmitted from the pulmonary artery23 into the pulmonary veins, then into the left ventricle of the heart, and from thence into the arteries24 of the body, but that this is effected by the ceaseless pulsation25 of the heart and the motion of the lungs in breathing.
There are, as everyone knows, three sigmoid or semilunar valves situated26 at the orifice of the pulmonary artery, which effectually prevent the blood sent into the vessel14 from returning into the cavity of the heart. Now Galen, explaining the use of these valves, and the necessity for them, employs the following language: 9 “There is everywhere a mutual27 anastomosis and inosculation of the arteries with the veins, and they severally transmit both blood and spirit, by certain invisible and undoubtedly28 very narrow passages. Now if the mouth of the pulmonary artery had stood in like manner continually open, and nature had found no contrivance for closing it when requisite29, and opening it again, it would have been impossible that the blood could ever have passed by the invisible and delicate mouths, during the contractions30 of the thorax, into the arteries; for all things are not alike readily attracted or repelled31; but that which is light is more readily drawn32 in, the instrument being dilated, and forced out again when it is contracted, than that which is heavy; and in like manner is anything drawn more rapidly along an ample conduit, and again driven forth33, than it is through a narrow tube. But when the thorax is contracted the pulmonary veins, which are in the lungs, being driven inwardly, and powerfully compressed on every side, immediately force out some of the spirit they contain, and at the same time assume a certain portion of blood by those subtle mouths, a thing that could never come to pass were the blood at liberty to flow back into the heart through the great orifice of the pulmonary artery. But its return through this great opening being prevented, when it is compressed on every side, a certain portion of it distils34 into the pulmonary veins by the minute orifices mentioned.” And shortly afterwards, in the next chapter, he says: “The more the thorax contracts, the more it strives to force out the blood, the more exactly do these membranes35 (viz., the semilunar valves) close up the mouth of the vessel, and suffer nothing to regurgitate.” The same fact he has also alluded36 to in a preceding part of the tenth chapter: “Were there no valves, a three-fold inconvenience would result, so that the blood would then perform this lengthened37 course in vain; it would flow inwards during the disastoles of the lungs and fill all their arteries; but in the systoles, in the manner of the tide, it would ever and anon, like the Euripus, flow backwards38 and forwards by the same way, with a reciprocating39 motion, which would nowise suit the blood. This, however, may seem a matter of little moment: but if it meantime appear that the function of respiration suffer, then I think it would be looked upon as no trifle, etc.” Shortly afterwards he says: “And then a third inconvenience, by no means to be thought lightly of, would follow, were the blood moved backwards during the expirations, had not our Maker40 instituted those supplementary41 membranes. “In the eleventh chapter he concludes: “That they (the valves) have all a common use, and that it is to prevent regurgitation or backward motion; each, however, having a proper function, the one set drawing matters from the heart, and preventing their return, the other drawing matters into the heart, and preventing their escape from it. For nature never intended to distress42 the heart with needless labour, neither to bring aught into the organ which it had been better to have kept away, nor to take from it again aught which it was requisite should be brought. Since, then, there are four orifices in all, two in either ventricle, one of these induces, the other educes43.” And again he says: “Farther, since there is one vessel, which consists of a simple covering implanted in the heart, and another which is double, extending from it (Galen is here speaking of the right side of the heart, but I extend his observations to the left side also), a kind of reservoir had to be provided, to which both belonging, the blood should be drawn in by one, and sent out by the other.”
Galen adduces this argument for the transit44 of the blood by the right ventricle from the vena cava into the lungs; but we can use it with still greater propriety45, merely changing the terms, for the passage of the blood from the veins through the heart into the arteries. From Galen, however, that great man, that father of physicians, it clearly appears that the blood passes through the lungs from the pulmonary artery into the minute branches of the pulmonary veins, urged to this both by the pulses of the heart and by the motions of the lungs and thorax; that the heart, moreover, is incessantly46 receiving and expelling the blood by and from its ventricles, as from a magazine or cistern47, and for this end it is furnished with four sets of valves, two serving for the induction48 and two for the eduction49 of the blood, lest, like the Euripus, it should be incommodiously sent hither and thither50, or flow back into the cavity which it should have quitted, or quit the part where its presence was required, and so the heart might be oppressed with labour in vain, and the office of the lungs be interfered51 with. 10 Finally, our position that the blood is continually permeating from the right to the left ventricle, from the vena cava into the aorta52, through the porosities of the lungs, plainly appears from this, that since the blood is incessantly sent from the right ventricle into the lungs by the pulmonary artery, and in like manner is incessantly drawn from the lungs into the left ventricle, as appears from what precedes and the position of the valves, it cannot do otherwise than pass through continuously. And then, as the blood is incessantly flowing into the right ventricle of the heart, and is continually passed out from the left, as appears in like manner, and as is obvious, both to sense and reason, it is impossible that the blood can do otherwise than pass continually from the vena cava into the aorta.
Dissection22 consequently shows distinctly what takes place in the majority of animals, and indeed in all, up to the period of their maturity53; and that the same thing occurs in adults is equally certain, both from Galen’s words, and what has already been said, only that in the former the transit is effected by open and obvious passages, in the latter by the hidden porosities of the lungs and the minute inosculations of vessels. It therefore appears that, although one ventricle of the heart, the left to wit, would suffice for the distribution of the blood over the body, and its eduction from the vena cava, as indeed is done in those creatures that have no lungs, nature, nevertheless, when she ordained54 that the same blood should also percolate the lungs, saw herself obliged to add the right ventricle, the pulse of which should force the blood from the vena cava through the lungs into the cavity of the left ventricle. In this way, it may be said, that the right ventricle is made for the sake of the lungs, and for the transmission of the blood through them, not for their nutrition; for it were unreasonable55 to suppose that the lungs should require so much more copious56 a supply of nutriment, and that of so much purer and more spirituous a nature as coming immediately from the ventricle of the heart, that either the brain, with its peculiarly pure substance, or the eyes, with their lustrous57 and truly admirable structure, or the flesh of the heart itself, which is more suitably nourished by the coronary artery.
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1
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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permeating
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| 弥漫( permeate的现在分词 )； 遍布； 渗入； 渗透 | |
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rivulets
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| n.小河，小溪( rivulet的名词复数 ) | |
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acidulous
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| adj.微酸的；苛薄的 | |
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concoction
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| n.调配(物)；谎言 | |
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percolate
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| v.过滤，渗透 | |
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credible
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| adj.可信任的，可靠的 | |
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assent
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| v.批准，认可；n.批准，认可 | |
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dense
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| a.密集的，稠密的，浓密的；密度大的 | |
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texture
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| n.(织物)质地；(材料)构造；结构；肌理 | |
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impelling
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| adj.迫使性的，强有力的v.推动、推进或敦促某人做某事( impel的现在分词 ) | |
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distension
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| n.扩张，膨胀(distention) | |
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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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vessel
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| n.船舶；容器，器皿；管，导管，血管 | |
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respiration
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| n.呼吸作用；一次呼吸；植物光合作用 | |
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precisely
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| adv.恰好，正好，精确地，细致地 | |
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remains
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| n.剩余物，残留物；遗体，遗迹 | |
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dilated
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| adj.加宽的，扩大的v.（使某物）扩大，膨胀，张大( dilate的过去式和过去分词 ) | |
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constricted
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| adj.抑制的，约束的 | |
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nourishment
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| n.食物，营养品；营养情况 | |
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skilful
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| (=skillful)adj.灵巧的，熟练的 | |
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dissection
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| n.分析；解剖 | |
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artery
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| n.干线，要道；动脉 | |
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arteries
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| n.动脉( artery的名词复数 )；干线，要道 | |
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pulsation
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| n.脉搏，悸动，脉动；搏动性 | |
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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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mutual
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| adj.相互的，彼此的；共同的，共有的 | |
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undoubtedly
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| adv.确实地，无疑地 | |
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requisite
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| adj.需要的，必不可少的；n.必需品 | |
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contractions
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| n.收缩( contraction的名词复数 )；缩减；缩略词；（分娩时）子宫收缩 | |
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repelled
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| v.击退( repel的过去式和过去分词 )；使厌恶；排斥；推开 | |
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drawn
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| v.拖，拉，拔出；adj.憔悴的，紧张的 | |
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forth
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| adv.向前；向外，往外 | |
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distils
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| v.蒸馏( distil的第三人称单数 )；从…提取精华 | |
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membranes
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| n.（动物或植物体内的）薄膜( membrane的名词复数 )；隔膜；（可起防水、防风等作用的）膜状物 | |
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alluded
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| 提及，暗指( allude的过去式和过去分词 ) | |
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lengthened
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| （时间或空间）延长，伸长( lengthen的过去式和过去分词 ) | |
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backwards
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| adv.往回地，向原处，倒，相反，前后倒置地 | |
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reciprocating
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| adj.往复的；来回的；交替的；摆动的v.报答，酬答( reciprocate的现在分词 )；（机器的部件）直线往复运动 | |
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maker
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| n.制造者，制造商 | |
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supplementary
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| adj.补充的，附加的 | |
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42
distress
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| n.苦恼，痛苦，不舒适；不幸；vt.使悲痛 | |
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43
educes
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| v.引出( educe的第三人称单数 )；唤起或开发出（潜能）；推断（出）；从数据中演绎（出） | |
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44
transit
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| n.经过，运输；vt.穿越，旋转；vi.越过 | |
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propriety
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| n.正当行为；正当；适当 | |
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incessantly
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| ad.不停地 | |
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cistern
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| n.贮水池 | |
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48
induction
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| n.感应，感应现象 | |
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49
eduction
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| n.引出；排出；推断；引出物 | |
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50
thither
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| adv.向那里；adj.在那边的，对岸的 | |
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51
interfered
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| v.干预( interfere的过去式和过去分词 )；调停；妨碍；干涉 | |
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aorta
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| n.主动脉 | |
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53
maturity
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| n.成熟；完成；(支票、债券等)到期 | |
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54
ordained
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| v.任命（某人）为牧师( ordain的过去式和过去分词 )；授予（某人）圣职；（上帝、法律等）命令；判定 | |
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unreasonable
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| adj.不讲道理的，不合情理的，过度的 | |
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copious
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| adj.丰富的，大量的 | |
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lustrous
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| adj.有光泽的；光辉的 | |
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