LETTER II
To Paul Marquard Slegel, of Hamburg
I congratulate you much, most learned sir, on your excellent commentary, in which you have replied in a very admirable manner to Riolanus, the distinguished anatomist, and, as you say, formerly your teacher: invincible truth has, indeed, taught the scholar to vanquish the master. I was myself preparing a sponge for his most recent arguments; but intent upon my work “On the Generation of Animals” (which, but just come forth, I send to you), I have not had leisure to produce it. And now I rather rejoice in the silence, as from your supplement I perceive that it has led you to come forward with your excellent reflections, to the common advantage of the world of letters. For I see that in your most ornate book (I speak without flattery), you have skilfully and nervously confuted all his machinations against the circulation, and successfully thrown down the scaffolding of his more recent opinions. I am, therefore, but little solicitous about labouring at any ulterior answer. Many things might, indeed, be adduced in confirmation of the truth, and several calculated to shed clearer light on the art of medicine; but of these we shall perhaps see further by and by.
Meantime, as Riolanus uses his utmost efforts to oppose the passage of the blood into the left ventricle through the lungs, and brings it all hither through the septum, and so vaunts himself upon having upset the very foundations of the Harveian circulation (although I have nowhere assumed such a basis for my doctrine; for there is a circulation in many red-blooded animals that have no lungs), it may be well here to relate an experiment which I lately tried in the presence of several of my colleagues, and from the cogency of which there is no means of escape for him. Having tied the pulmonary artery, the pulmonary veins, and the aorta, in the body of a man who had been hanged, and then opened the left ventricle of the heart, we passed a tube through the vena cava into the right ventricle of the heart, and having, at the same time, attached an ox’s bladder to the tube, in the same way as a clyster-bag is usually made, we filled it nearly full of warm water, and forcibly injected the fluid into the heart, so that the greater part of a pound of water was thrown into the right auricle and ventricle. The result was, that the right ventricle and auricle were enormously distended, but not a drop of water or of blood made its escape through the orifice in the left ventricle. The ligatures having been undone, the same tube was passed into the pulmonary artery, and a tight ligature having been put round it to prevent any reflux into the right ventricle, the water in the bladder was now pushed towards the lungs, upon which a torrent of the fluid, mixed with a quantity of blood, immediately gushed forth from the perforation in the left ventricle; so that a quantity of water, equal to that which was pressed from the bladder into the lungs at each effort, instantly escaped by the perforation mentioned. You may try this experiment as often as you please; the result you will still find to be as I have stated it.
With this one experiment you may easily put an end to all Riolanus’s altercations on the matter, to which he, nevertheless, so entirely trusts, that, without adducing so much as a single experiment in support of his views, he has been led to invent a new circulation, and even so far to commit himself as to say that, unless the old doctrine of the circulation[56] be overturned, his own is inadmissible. We may pardon this distinguished individual for not having sooner discovered a hidden truth; but that he, so well skilled in anatomy as he is, should obstinately contend against a truth illustrated by the clearest light of reason, this surely is argument of his envy—let me not call it by any worse name. But, perhaps, we are still to find an excuse for Riolanus, and to say, that what he has written is not so much of his own motion, as in discharge of the duties of his office, and with a view to stand well with his colleagues. As Dean of the College of Paris, he was bound to see the physic of Galen kept in good repair, and to admit no novelty into the school, without the most careful winnowing, lest, as he says, the precepts and dogmata of physic should be disturbed, and the pathology which has for so many years obtained the sanction of all the learned in assigning the causes of disease, be overthrown. He has been playing the part of the advocate, therefore, rather than of the practised anatomist. But, as Aristotle tells us, it is not less absurd to expect demonstrative arguments from the advocate, than it is to look for persuasive arguments from the demonstrator or teacher. For the sake of the old friendship subsisting between us, moreover, and the high praise which he has lavished on the doctrine of the circulation, I cannot find it in my heart to say anything severe of Riolanus.
I therefore return to you, most learned Slegel, and say, that I wish greatly I had been so full and explicit in what I have said on the subject of anastomosis in my disquisition to Riolanus, as would have left you with no doubts or scruples on the matter. I could wish, also, that you had taken into account not only what I have there denied, but likewise what I have asserted on the transference of the blood from the arteries into the veins; especially as I there seem to have pointed out some cause both for my inquiry and for my negation, to hint at a certain cause. I confess, I say, nay, I even pointedly assert, that I have never found any visible anastomoses. But this was particularly said against Riolanus, who limited the circulation of the blood to the larger vessels only, with which, therefore, these anastomoses, if any such there were, must have been made conformable, viz. of ample size, and distinctly visible. Although it be true, therefore, that I totally deny all anastomoses of this description—anastomoses in the way the word is commonly understood, and as the meaning has come down to us from Galen, viz. a direct conjunction between the orifices of the [visible] arteries and veins—I still admit, in the same disquisition, that I have found what is equivalent to this in three places, namely, in the plexus of the brain, in the spermatic or preparing arteries and veins, and in the umbilical arteries and veins. I shall now, therefore, for your sake, my learned friend, enter somewhat more at large into my reasons for rejecting the vulgar notion of the anastomoses, and explain my own conjectures concerning the mode of transition of the blood from the minute arteries into the finest veins.
All reasonable medical men, both of ancient and modern times, have believed in a mutual transfusion, or accession and recession of the blood between the arteries and the veins; and for the sake of permitting this, they have imagined certain inconspicuous openings, or obscure foramina, through which the blood flowed hither and thither, moving out of one vessel and returning to it again. Wherefore it is not wonderful that Riolanus should in various places find that in the ancients which is in harmony with the doctrine of a circulation. For a circulation in such sort teaches nothing more than that the blood flows incessantly from the veins into the arteries, and from the arteries back again into the veins. But as the ancients thought that this movement took place indeterminately, by a kind of accident, in one and the same place, and through the same channels, I imagine that they therefore found themselves compelled to adopt a system of anastomoses, or fine mouths mutually conjoined, and serving both systems of vessels indifferently. But the circulation which I discovered teaches clearly that there is a necessary outward and backward flow of the blood, and this at different times and places, and through other and yet other channels and passages; that this flow is determinate also, and for the sake of a certain end, and is accomplished in virtue of parts contrived for the purpose with consummate forecast and most admirable art. So that the doctrine of the motion of the blood from the veins into the arteries, which antiquity only understood in the way of conjecture, and which it also spoke of in confused and indefinite terms, was laid down by me with its assured and necessary causes, and presents itself to the understanding as a thing extremely clear, perfectly well arranged, and of approved verity. And then, when I perceived that the blood was transferred from the veins into the arteries through the medium of the heart with singular art, and with the aid of an admirable apparatus of valves, I imagined that the transference from the extremities of the arteries into those of the veins could not be effected without some other admirable artifice, at least wherever there was no transudation through the pores of the flesh. I therefore held the anastomoses of the ancients as fairly open to suspicion, both as they nowhere presented themselves to our eyes, and as no sufficient reason was alleged for anything of the kind.
Since, then, I find a transit from the arteries into the veins in the three places which I have above mentioned, equivalent to the anastomoses of the ancients, and even affording the farther security against any regurgitation into the arteries of the blood once delivered to the veins, and as a mechanism of such a kind is more elaborate and better suited to the circulation of the blood, I have therefore thought that the anastomoses imagined by the ancients were to be rejected. But you will ask, what is this artifice? what these ducts? viz. the small arteries, which are always much smaller—twice, even three times smaller—than the veins which they accompany, which they approach continually more and more, and within the tunics of which they are finally lost. I have been therefore led to conceive that the blood brought thus between the coats of the veins advanced for a certain way along them, and that the same thing took place here which we observe in the conjunction between the ureters and the bladder, and of the biliary duct with the duodenum. The ureters insinuate themselves obliquely and tortuously between the coats of the bladder, without anything in the nature of an anastomosis, yet in such a manner as occasionally affords a passage to blood, to pus, and to calculi; it is easy, moreover, to fill the bladder through them with air or water; but by no effort can you force anything from the bladder into them. I care not, however, to make any question here of the etymology of words; for I am not of opinion that it is the province of philosophy to infer aught as to the works of nature from the signification of words, or to cite anatomical disquisitions before the grammatical tribunal. Our business is not so much to inquire what a word properly signifies, as how it is commonly understood; for use and wont, as in so many other matters, are greatly to be considered in the interpretation of words. It seems to me, therefore, that we are to take especial care not to employ any unusual words, or any common ones already familiarly used, in a sense which is not in accordance with the meaning we purpose to attach to them. You indeed counsel well when you say, “only make sure of the thing, call it what you will.” But when we discover that a thing has hitherto been indifferently or incorrectly explained (as the sequel will show it to have been in the present case), I do not think that the old appellation can ever be well applied to the new fact; by using the old term you are apt to mislead where you desire to instruct. I acknowledge, then, a transit of the blood from the arteries into the veins, and that occasionally immediate, without any intervention of soft parts; but it does not take place in the manner hitherto believed, and as you yourself would have it, where you say that anastomoses, correctly speaking, rather than an anastomosis, were required, namely, that the vessels may be open on either hand, and give free passage to the blood hither and thither. And hence it comes that you fail in the right solution of the question, when you ask how it happens that with the arteries as patent or pervious as the veins, the blood nevertheless flows only from the former into the latter, never from the latter into the former? For what you say of the impulse of the blood through the arteries does not fully solve the difficulty in the present instance. For if the aorta be tied near the left ventricle of the heart in a living animal, and all the blood removed from the arteries, the veins are still seen full of blood; so that it neither moves back spontaneously into the arteries, nor can it be repelled into these by any force, whilst even in a dead animal it nevertheless falls of its own accord through the finest pores of the flesh and skin from superior into inferior parts. The passage of the blood into the veins is, indeed, effected by the impulse in question, and not by any dilatation of these in the manner of bellows, by which the blood is drawn towards them; but there are no anastomoses of the vessels by conjunction (per copulam), in the way you mention, none where two vessels meeting are conjoined by equal mouths. There is only an opening of the artery into the vein, exactly in the same manner as the ureter opens into the bladder (and the biliary duct opens into the jejunum), by which, whilst the flow of urine is perfectly free towards the bladder, all reflux into the smaller conduits is effectually prevented; the fuller the bladder is, indeed, the more are the sides of the ureters compressed, and the more effectual is all ascent of urine in them prevented. Now, on this hypothesis, it is easy to render a reason for the experiment which I have already mentioned. I add further, that I can in nowise admit such anastomoses as are commonly imagined, inasmuch as the arteries being always much smaller than the veins, it is impossible that their sides can mutually conjoin in such a way as will allow of their forming a common meatus; it seems matter of necessity that things which join in this way should be of equal size. Lastly, these vessels having made a certain circuit, must, at their terminations, encounter one another; they would not, as it happens, proceed straight to the extremities of the body. And the veins, on their part, if they were conjoined with the arteries by mutual inosculations, would necessarily, and by reason of the continuity of parts, pulsate like the arteries.
And now, that I may make an end of my writing, I say, that whilst I think the industry of every one deserving of commendation, I do not remember that I have anywhere bepraised mine own. You, however, most excellent sir, I conceive have deserved high commendation, both for the care you have bestowed on your disquisition on the liver of the ox, and for the judgment you display in your observations. Go on, therefore, as you are doing, and grace the republic of letters with the fruits of your genius, for thus will you render a grateful service to all the learned, and especially to
Your loving
William Harvey.
Written in London, this 26th of March, 1651.