Rightly then is it observed by Fabricius,[387]that “this fleshystructure, differs much in shape, size, position, and number in different kinds of animals. The human female has one placenta only; as is the case with the mouse, rabbit, guinea-pig, dog, and cat:” so also with many animals which have the toes distinct, and incisor teeth in both jaws. “All those which have the hoof cloven and incisors in one jaw only, have several placentæ, whether they be domesticated animals, like the sheep, cow, and goat, or wild, as the red-deer, roe, fallow-deer, and others of the same kind. Again, where there is only one of these fleshy structures it either resembles a cake, (whence its name placenta), as in the human female, rabbit, hare, mole, mouse, and guinea-pig; or else it is like a girdle or bandage encircling the trunk of the body, as in the dog, cat, ferret, and the like.” In some it resembles the cup or chalice of the acorn, and surrounds the greater part of the “conception,” as in the hare and rabbit, its convex part adhering to the uterus, the concave looking towards the fœtus. “Again, in animals which have this structure in the form of a cake, although the shape is similar, the situation in which it is found is very different. In the human female it adheres to the fundus of the uterus, and is as far removed from the fœtus as possible, their connexion being effected by means of long vessels. In the mouse, guinea-pig, and rabbit, it is attached partly in the region of the loins, partly at the sides of the thorax. Those animals which have numerous placentæ are all furnished with incisors in one jaw only, as the sheep, cow, goat, red-deer, roe, and the like. Yet in these some variety is observable.”
For in the sheep the carunculæ are many in number, and of different magnitudes, the largest being of the size of a nutmeg, the smallest of that of a pea or vetch: they are also of a rounded form and reddish hue, with their convex portion turned towards the uterus, something in the semblance of soft warts or nipples. “In the cow they are larger, wider, and whiter, more like a spongy or fungoid body,” and they appear to take their origin from the chorion. In the red or fallow-deer they are five only in number; these spring from the walls of the uterus, and thrust themselves inwards, exhibiting their depressions or acetabula on the side of the fœtus. But in all animals it is observed that the carunculæ adhere firmly to the uterus, and cannot be separated from it without considerable difficulty,except at the period of birth; at which time they become loosened from their attachments and fall like ripe fruit. If they are forcibly torn from the uterus, I have observed the greater part of the blood that escapes to flow, not from the “conception,” but from the uterus itself.
Fabricius,[388]when discussing the mode of union between the “fleshy substance” and the uterus, uses many arguments, but in my opinion weak ones, to prove that the umbilical vessels anastomose with those of the uterus: yet he seems chiefly to have done so to countenance the old opinion once held almost by all; for he confesses that he can make no positive assertion on the subject, “because the fleshy mass itself stands in the way of any accurate investigation.” Yet neither reason nor observation would lead us to believe that more anastomoses exist in the uterus, than in the liver between the branches of the vena portæ and the cava; or in the mamma, between the vessels which transmit blood and those which carry milk. There may be, indeed, at places a juxtaposition of vessels, and sometimes the insertion of one into the coats of another; but the perfect coalition and union, described by Fabricius, never exist. Were it so, the veins and arteries ought to be continuous; for the vessels which bring the blood from the mother into the uterus and carunculæ are arteries, whilst those which pass from the uterus to the fœtus are veins, as is readily apparent; for they carry blood from the placenta into the vena cava.
Hence the opinion of Arantius seems to me to be the true one, viz. that the orifices of the umbilical veins are in no way continuous with the uterine vessels. For there is a smaller number of vessels carrying blood to the uterus than there is of veins returning it to the fœtus; and the greater part of the roots of those terminate in the chorion. Yet Fabricius, either from respect to the ancients, or through an envious feeling towards Arantius, most pertinaciously holds to the old opinion.
Fabricius[389]has ascertained nothing on the subject of the “cotyledons” or “acetabula;” he gives only the various opinions of the ancients. In the former part of my work, however, in the history of the fœtus in the deer, I have mentioned the animals in which acetabula are found; at the same time I described them as constituting numerous cells of a small size scattered throughout the carunculæ, or “fleshy substance,” and filled with an albuminous or mucilaginous fluid, like a honeycomb full of honey.
In the deer they greatly resemble in shape the cavity of the haunch-bone which receives the head of the thigh; hence their name in Greek, κοτυλήδονες (little measures); and in Latin, acetabula, because they resemble the little cups formerly brought to table filled with vinegar for sauce.
These cavities do not exceed in size the holes in a large sponge, and a delicate ramification of the umbilical vessels penetrates deeply into each of them; for in them aliment is laid up for the fœtus, not indeed constituted of blood, as Fabricius would have it, but matter of a mucous character, and greatly resembling the thicker part of the albumen in the egg. Hence it is clear, as I have before observed, that the fœtus in cloven-footed animals (as indeed in all others) is not nourished by the blood of the mother.
Aristotle’s[390]statement, “that the acetabula gradually diminish with the growth of the fœtus, and at last disappear,” is not borne out by experiment; for as the fœtus increases so do the carunculæ; the acetabula at the same time become more capacious and numerous, and more full of the albuminous matter.
If the carunculæ are pressed no blood escapes, but just as water or honey can be squeezed from a sponge or honeycomb, so if pressure is made a whitish fluid oozes from out of the acetabula, which then become shrunk, white, and flaccid, and at last come to resemble a nipple, or a large flabby wart.
Aristotle asserts, with truth, that acetabula are not found in all animals; for they do not exist in the woman, nor (as far as I know) in any animal which possesses a single fleshy substance or placenta. As to the uses of the carunculæ, I believe that, like the mamma, they elaborate not blood but a fluid resembling albumen, and that this serves for the nourishment of the fœtus.
Fabricius gives an elegant description, as well as most beautiful figures, of the umbilical vessels. “The veins,” he says,[391]“which pass from the uterus in the direction of the fœtus are always closely united and become larger and larger as they proceed; nor does this mutual interlacement cease until all end in two large trunks; these penetrate the fœtus at the umbilicus, and become one vein of great size, which is inserted into the liver of the fœtus, and has a communication both with the vena cava and vena portæ. In like manner the arteries which accompany the veins, being many in number and exceedingly minute, pass from the uterus towards the fœtus, and, gradually uniting and increasing in size, terminate in two large trunks; these, after penetrating the umbilicus, separate from the veins, and attaching themselves to the lateral surface of the bladder by the intervention of a membrane, proceed downwards on either side and become continuous with the branches of the aorta descending to the thigh.” It must be observed, however, that this description of Fabricius applies only to the umbilical vessels of the human fœtus, and not to the young of every animal. Nor even does it hold in the case of the human fœtus except when it is full grown; for at the beginning the arteries make little show, and are so small as to require the eyes of a lynx to see them; nor afterwards indeed are they distinguishable except by their pulsation: in other particulars they resemble veins. Since then, as I have elsewhere shown, the very small branches of arteries do not pulsate, in so far as the eye is concerned, there can be no difference between them and veins. The arteries, I say, at this time are so fine andminute, that they are woven, as it were, like the most delicate threads, into the tissues of the veins, or rather in some obscure manner insinuate themselves into them; hence they almost entirely elude the sight. But all the veins, by a retrograde movement, unite their twigs and terminate in one trunk like the branches of a tree, in the same manner as the mesenteric veins, all of which terminate in the vena portæ.
Near the embryo [the umbilical veins] are divided into two trunks, but when entered within it they constitute one umbilical vein, which ends in the vena cava, near the right auricle of the heart, and passes through the liver, entering the vena portæ; giving off no branches besides until it leaves the convex portion of the liver by a very large orifice. So that if the vena cava is opened from the right auricle downwards and emptied of blood, three apertures may be seen close to each other; one is the entrance of the vena cava descendens, the second that of the hepatic vein, which ramifies throughout the convex portion of the liver, and the third is the origin of the umbilical vein. Hence it is quite clear that the origin of the veins is by no means to be looked for in the liver; inasmuch as the orifice of the vena cava descendens is much larger than the hepatic branch, which is indeed equalled in size by the umbilical vein. For the branches are not said to be the origin of their trunk; but where the trunk is greatest there the origin of the veins is to be looked for, and this is the case at the entrance of the right ventricle: here, then, the origin of all veins, and the storehouse of the blood must be placed.
To return to the umbilical vessels, which are not subdivided in the same way in all animals; for in some two or more branches of veins are found within the body of the fœtus,—some of which pass through the liver, whilst others join the portal and mesenteric veins. In the human fœtus, at a distance of three or four fingers’ breadth from the umbilicus, the trunks of the arteries and veins are involved together in a complicated manner, (as if one were to twist several waxen tapers in the form of a stick,) and are besides covered and held together by a thick gelatinous membrane. This cord passes on towards the chorion, and when arrived at the concave portion of the placenta and the inner surface of the chorion, splits into innumerable branches; these divide again, and constitutethe means by which the nutrient matter is taken up, as by rootlets, and distributed to the fœtus. The veins of the cord are marked at various places by knots or varices, resembling vesicles filled with blood; this is a contrivance of nature to prevent the blood rushing too violently to the fœtus. From the number of these knots superstitious midwives are accustomed to predict the number of the future offspring; and if none can be seen at all they pronounce that the woman will be ever after barren: they also absurdly prophesy by the distance between the knots about the interval to take place between the birth of each child, and also of its sex from their colour.
A like arrangement of the umbilical vessels is found in almost all fœtuses furnished with a single placenta, as in the dog, mouse, and others; but in these the cord is shorter and less convoluted. In the ox, sheep, red-deer, fallow-deer, hog, and others, in which the nutrient material is not supplied from one fleshy mass or placenta, but from several, the umbilical vessels are distributed in a different manner. The branches and extremities of these vessels are not only disseminated through the fleshy substance, but still more and chiefly through the membrane of the chorion itself by means of the most delicate fibres; exactly in the same way as the vessels are distributed in the human fœtus, without the aid of the cord, before the “conception” adheres to the uterus. Hence it is plain that the embryo does not derive all its nourishment from the placenta, but receives a considerable portion of it from the fluid contained in the chorion.
As to the uses of the umbilical vessels, I cannot agree with Fabricius, for he imagines that all the blood is supplied to the fœtus from the uterus by means of the veins, and that the vital spirits are transmitted from the mother by the arteries. He also asserts that no part of the fœtus performs any common function, but that each individual portion looks only to itself, how it may be nourished, grow, and be preserved. In like manner, because he has found no nerve in the umbilical cord, he refuses to allow sensation or voluntary motion to the fœtus. Just as if the uterus or placenta of the mother were the heart or first source whence these functions are derived to the fœtus, and whence heat flows in and is distributed through all its parts. All these are manifest errors. For the human fœtus, evenbefore the completion of the fourth month, (in some animals sooner,) in no obscure manner moves, rolls about, and kicks, especially if it suffer from cold, heat, or any external source of inconvenience. Moreover, the “punctum saliens” (whilst yet the heart is not) moves to and fro, with an evident pulsation, and distributes blood and spirits; and this part, as I have before stated, if languid and nearly extinct through cold, will, if warmth be applied, again be restored and live. In the Cæsarean section, also, it is quite clear that the life of the embryo does not immediately depend upon the mother, and that the spirits do not proceed from her; for I have often seen the fœtus extracted alive from the uterus when the mother has been dead some hours. I have also known the rabbit and hare survive when extracted from the uterus of the dead mother. Besides, in a tedious labour we learn whether the infant is alive or not by the pulsation of the umbilical arteries; and it is certain that these arteries receive their impulse from the heart of the fœtus and not of the mother, for the rhythm of the two differs: this can be easily ascertained if one hand is applied to the wrist of the mother and the other to the umbilical cord. Nay, in the Cæsarean section, when the embryo is still enveloped in the chorion, I have often found the umbilical arteries pulsating, and the fœtus lively, even when the mother was dead and her limbs stiffened. It is not, therefore, true that the “spirits” pass from the mother to the fœtus through the arteries; nor is it more so that the umbilical or fœtal vessels anastomose with those of the uterus. The fœtus has a proper life of its own, and possesses pulsating arteries filled with blood and “spirits,” long before the “conception,” in which it is formed and dwells, is attached to the uterus; just as it is with the chick in the egg.
In my treatise on the Circulation of the Blood I have shown the uses of the arteries, both in the fœtus and in the adult, to be very different from what is generally supposed, and my views receive confirmation from the subject now under consideration.
In truth, the “secundines” are part of the “conception,” and depend upon it, borrowing thence their life and faculty of growth. For, just as in the mesentery, the blood is propelled to the intestines by the branches of the cœliac and mesentericarteries, and returns thence by means of the veins to the liver and heart, together with the chyle, so in like manner do the umbilical arteries carry the blood to the secundines; which blood, together with the nutrient fluid, is brought back by the veins to the fœtus. Hence it is that these arteries do not proceed immediately from the heart, as if they were the principal vessels, but take their origin from the arteries of the lower limbs, as being of inferior rank, use, and magnitude.
Adrian Spigelius lately published a book entitled ‘On the Formation of the Fœtus’ (de Formato Fœtu); in which he treats of the uses of the umbilical arteries, and proves, by powerful arguments, that the fœtus does not receive vital “spirits” from the mother through the arteries; he also answers fully the arguments on the other side. He could also have shown by the same arguments that neither is the blood transferred to the fœtus from the vessels of the mother by means of the branches of the umbilical veins; this is especially clear from the case of the hen’s egg, and also of the Cæsarean section. In truth, if heat and life flow to the blood from the mother, should she die the child must straightway be destroyed also, for the same fatality must attach to both; nay, the child must be the first to perish; for as dissolution approaches, the subordinate parts languish and grow chill before the principal ones, and so the heart fails last of all. The blood, I mean of the fœtus, would be the first to lose its heat and become unfit to perform its functions were it derived from the uterus, since the uterus would be deprived of all vital heat before the heart.
Fabriciushas indeed recounted many wonderful things on the subject of parturition; for my own part, I think there is more to admire and marvel at in conception. It is a matter, in truth, full of obscurity; yet will I venture to put forth a few things—rather though as questions proposed for solution—that I may not appear to subvert other men’s opinions only, without bringing forward anything of my own. Yet what I shall state I wish not to be taken as if I thought it a voice from an oracle, or desired to gain the assent of others by violence; I claim, however, that liberty which I willingly yield to others, the permission, viz. in subjects of difficulty to put forward as true such things as appear to be probable until proved to be manifestly false.
It is to the uterus that the business of conception is chiefly intrusted: without this structure and its functions conception would be looked for in vain. But since it is certain that the semen of the male does not so much as reach the cavity of the uterus, much less continue long there, and that it carries with it a fecundating power by a kind of contagious property, (not because it is then and there in actual contact, or operates, but because it previously has been in contact); the woman, after contact with the spermatic fluid in coitu, seems to receive influence, and to become fecundated without the co-operation of any sensible corporeal agent, in the same way as iron touched by the magnet is endowed with its powers and can attract other iron to itself. When this virtue is once received the woman exercises a plastic power of generation, and produces a being after her own image; not otherwise than the plant, which we see endowed with the forces of both sexes.
Yet it is a matter of wonder where this faculty abides after intercourse is completed, and before the formation of the ovum or “conception.” To what is this active power of the male committed? is it to the uterus solely, or to the whole woman? or is it to the uterus primarily and to the woman secondarily? or, lastly, does the woman conceive in the womb, as we see by the eye and think by the brain?
For although the woman conceiving after intercourse sometimes produces no fœtus, yet we know that phenomena occur which clearly indicate that conception has really taken place, although without result. Over-fed bitches, which admit the dog without fecundation following, are nevertheless observed to be sluggish about the time they should have whelped, and to bark as they do when their time is at hand, also to steal away the whelps from another bitch, to tend and lick them, and also to fight fiercely for them. Others have milk or colostrum, as it is called, in their teats, and are, moreover, subject to the diseases of those which have actually whelped; the same thing is seen in hens which cluck at certain times, although they have no eggs on which to sit. Some birds also, as pigeons, if they have admitted the male, although they lay no eggs at all, or only barren ones, are found equally sedulous in building their nests.
The virtue which proceeds from the male in coitu has such prodigious power of fecundation, that the whole woman, both in mind and body, undergoes a change. And although it is the uterus made ready for this, on which the first influences are impressed, and from which virtue and strength are diffused throughout the body, the question still remains, how it is that the power thus communicated remains attached to the uterus? is it to the whole uterus or only to a part of it? nothing is to be found within it after coitus, for the semen in a short time either falls out or evaporates, and the blood, its circle completed, returns from the uterus by the vessels.
Again, what is this preparation or maturity of the uterus which eagerly demands the fecundating seed? whence does it proceed? Certain it is, unless the uterus be ready for coition every attempt at fecundation is vain; nay, in some animals, at no other time is the male admitted. It happens occasionally, I allow, that this maturity arrives earlier in some from thesolicitations of the male animal; it is itself, however, a purely natural result, just as is the ripening of the fruit in trees. What these changes are I will now recount, as I have found them by observation.
The uterus first appears more thick and fleshy; then its inner surface, the future residence, that is, of the “conception,” becomes softer, and resembles in smoothness and delicacy the ventricles of the brain; this I have already described in the deer and other cloven-footed tribes. But in the dog, cat, and other multiparous and digitated animals, the horns of the uterus—clearly corresponding to the round tubes of the woman [Fallopian tubes], the appendices of the intestines in birds, or the ureters in man—exhibit little protuberances at certain intervals, which swell up and become extremely soft; these, after intercourse, appear to open themselves, (as I have observed in deer;) from them the first white fluid transudes into the uterus, and out of this the “conception,” or ovum, is formed. In this way the uterus, by means of the male, (like fruit by the summer’s heat,) is brought to the highest pitch of maturity, and becomes impregnated.
But since there are no manifest signs of conception before the uterus begins to relax, and the white fluid or slender threads (like the spider’s web) constituting the “primordium” of the future “conception,” or ovum, shows itself; and since the substance of the uterus, when ready to conceive, is very like the structure of the brain, why should we not suppose that the function of both is similar, and that there is excited by coitus within the uterus a something identical with, or at least analogous to, an “imagination” (phantasma) or a “desire” (appetitus) in the brain, whence comes the generation or procreation of the ovum? For the functions of both are termed “conceptions,” and both, although the primary sources of every action throughout the body, are immaterial, the one of natural or organic, the other of animal actions; the one (viz. the uterus) the first cause and beginning of every action which conduces to the generation of the animal, the other (viz. the brain) of every action done for its preservation. And just as a “desire” arises from a conception of the brain, and this conception springs from some external object of desire, so also from the male, as being the more perfect animal, and, as it were, the mostnatural object of desire, does the natural (organic) conception arise in the uterus, even as the animal conception does in the brain.
From this desire, or conception, it results that the female produces an offspring like the father. For just as we, from the conception of the “form” or “idea” in the brain, fashion in our works a form resembling it, so, in like manner, the “idea,” or “form,” of the father existing in the uterus generates an offspring like himself with the help of the formative faculty, impressing, however, on its work its own immaterial “form.” In the same way art, which in the brain is the εἶδος or “form” of the future work, produces, when in operation, its like, and begets it out of “matter.” So too the painter, by means of conception, pictures to himself a face, and by imitating this internal conception of the brain carries it out into act; so also the builder constructs his house according to previous conception. The same thing takes place in every other action and artificial production. Thus, what education effects in the brain, viz. art, with its analogue does the coitus of the male endow the uterus, viz. the plastic art; hence many similar or dissimilar fœtuses are produced at the same coitus. For if the productions and first conceptions of art (the mere imitations of nature) are in this way formed in the brain, how much more probable is it that copies (exemplaria) of animal generation and conception should in like manner be produced in the uterus?
And since Nature, all of whose works are wonderful and divine, has devised an organ of this kind, viz. the brain, by the virtue and sensitive faculty of which the conceptions of the rational soul exist, such as the desires and the arts, the first principles and causes of so many and such various works, of which man, by means of the impulsive faculty of the brain, is by imitation the author; why should we not suppose that the same Nature, who in the uterus has constructed an organ no less wonderful, and adapted it by means of a similar structure to perform all that appertains to conception, has destined it for a similar or at least an analogous function, and intended an organ altogether similar for a similar use? For as the skilful artificer accomplishes his works by ingeniously adapting his instruments to each, so that from the substance and shape of theseinstruments it is easy to judge of their use and application, with no less certainty than we have been taught by Aristotle[392]to recognize the nature of animals from the structure and arrangement of their bodily organs; and as physiognomy instructs us to judge of a man’s disposition and character from the shape of his face and features, what should prevent us from supposing that where the same structure exists there is the same function implanted?
But it is so unfairly ordered that, when customary and familiar matters come to be debated, this very familiarity lessens their importance and our wonder; whilst things of much less moment, because they are novel and rare, appear to us far greater objects of marvel. Whoever has pondered with himself how the brain of the artist, or rather the artist by means of his brain, pictures to the life things which are not present to him, but which he has once seen; also in what manner birds immured in cages recall to mind the spring, and chant exactly the songs they had learned the preceding summer, although meanwhile they had never practised them; again, and this is more strange, how the bird artistically builds its nest, the copy of which it had never seen, and this not from memory or habit, but by means of an imaginative faculty (phantasia), and how the spider weaves its web, without either copy or brain, solely by the help of this imaginative power; whosoever, I say, ponders these things, will not, I think, regard it as absurd or monstrous, that the woman should be impregnated by the conception of a general immaterial “idea,” and become the artificer of generation.
I know well that some censorious persons will laugh at this,—men who believe nothing true but what they think so themselves. Yet this that I do is the practice of philosophers, who, when they cannot clearly comprehend how a thing really is brought to pass, devise some mode for it in accordance with the other works of nature, and as near as possible to what is true. And indeed all those opinions which we now regard as of the greatest weight, were at the beginning mere figments and imaginations, until confirmed by experiments addressed to the senses, and made credible by a knowledge of their positive causes. Aristotle[393]says “that philosophers are in some sort lovers of fables, seeing that fable is made up of marvels.” And indeed men were first led to cultivate philosophy from wondering at what they saw. For my own part, then, when I see nothing left in the uterus after intercourse to which I can ascribe the principle of generation, any more than there is in the brain anything discoverable after sensation and experience, which are the prime sources of art, and when I find the structure of both alike, I have devised this fable. Let learned and ingenious men consider of it, let the supercilious reject it, and those who are peevish and scoffing laugh if they please.
Since, then, nothing can be apprehended by the senses in the uterus after coition, and since it is necessary that there be something to render the female fruitful, and as this is probably not material, it remains for us to take refuge in the notion of a mere conception and of “species without matter” (species sine materiâ), and imagine that the same thing happens here as every one allows takes place in the brain, unless indeed there be some one “whom the gods have moulded of better clay,” and made fit to discover some other efficient cause besides any of those enumerated.
Some philosophers of our time have returned to the old opinion about atoms, and so imagine that this generative contagion, as indeed all others, proceeds from the subtile emanations of the semen of the male, which rise like odorous particles, and gain an entrance into the uterus at the period of intercourse. Others invoke to their aid incorporeal spirits, such as demiurgi, angels, and demons. Others regard it as a process of fermentation. Others devise other theories. I pray, therefore, a place for this conjecture of mine until something certain is established in the matter.
Many observations have been made by me which would easily overthrow the opinions I have mentioned, so easy is it to say what a thing is not rather than what it is; this is not, however, the place to introduce them, although elsewhere it is my intention to do so. On the present occasion I shall only observe, if that which is called by the common name of “contagion,” as arising from the contact of the spermatic fluid inintercourse, and which remains in the woman (without the actual presence of the semen) as the efficient of the future offspring—if, I say, this contagion (whether it be atoms, odorous particles, fermentation, or anything else) is not of the nature of any corporeal substance, it follows of necessity that it is incorporeal. And if on further inquiry it should appear that it is neither spirit nor demon, nor soul, nor any part of the soul, nor anything having a soul, as I believe can be proved by various arguments and experiments, what remains, since I am unable myself to conjecture anything besides, nor has any one imagined aught else even in his dreams, but to confess myself at a stand-still? “For whoever,” says Aristotle,[394]“doubts and wonders, confesses his ignorance; therefore if to escape the imputation of ignorance, ingenious men have turned to philosophy, it is clear they follow their pursuit for the sake of knowledge, and not from any other motive.”
It must not, then, be imputed to me for blame, if, eager for knowledge, and approaching untrodden ground, I have presented aught which at first sight may appear made up or fabulous. For as everything is not to be received at once with an unthinking credulity, so that which has been long and painfully considered must not be straightway rejected, even although it fail to catch the eye of the quick-sighted. Aristotle himself wrote a book, ‘De Mirabilibus audits,’ on hearsay wonders; and elsewhere he says,[395]“We must not only thank those in whose opinions we acquiesce, but those also who have said aught (to the purpose) although superficially. For these bring in something to the common stock, in this, that they exercise and train our habits. For if Timotheus had not existed, we should have lost much music. Yet if Phrynis had not been we should have had no Timotheus. So is it with those who have laid down any truth. For we have received some opinions from certain philosophers, yet were there others to whom these owed their existence.”
Influenced, then, by the example and authority of so great a man, and not to appear resolute only to subvert the doctrines of others, I have preferred proposing a fanciful opinion rather than none at all, playing in this the part of Phrynis toTimotheus, my object being to shake off the sloth of the age we live in, to rouse the intellects of the studious, and, rather than that the diligent investigator of nature should accuse me of indolence, to bid him laugh at my ill-formed and crude notions.
In truth, there is no proposition more magnificent to investigate or more useful to ascertain than this: How are all things formed by an “univocal” agent? How does the like ever generate the like? And this not only in productions of art (for so house builds house, face designs face, and image forms image), but also in things relating to the mind, for mind begets mind, opinion is the source of opinion. Democritus with his atoms, and Eudoxus with his chief good which he placed in pleasure, impregnated Epicurus; the four elements of Empedocles, Aristotle; the doctrines of the ancient Thebans, Pythagoras and Plato; geometry, Euclid. By this same law the son is born like his parents, and virtues which ennoble and vices which degrade a race are sometimes passed on to descendants through a long series of years. Some diseases propagate their kind, as lepra, gout, syphilis, and others. But why do I speak of diseases, when the moles, warts, and cicatrices of the progenitor are sometimes repeated in the descendant after many generations?[396]“Every fourth birth,” says Pliny,[397]“the mark of the origin of the Dacian family is repeated on the arm.” Why may not the thoughts, opinions, and manners now prevalent, many years hence return again, after an intermediate period of neglect? For the divine mind of the Eternal Creator, which is impressed on all things, creates the image of itself in human conceptions.
Having, therefore, overcome some difficulties relating to the subject, I feel a greater desire to enter into it a little more closely, and this with two objects in view—first, that what I have hitherto treated cursorily may seem to carry with it a greater weight of probability; and secondly, to stir up the intellects of the studious to search more deeply into so obscure a subject.
To illustrate the matter, let A stand for the fecundated egg (the “matter” that is of the future chick), which is alterable orconvertible into the chick, and is in fact the chicken in posse. Let B be that which fecundates the egg, and thus distinguishes it from an unfruitful egg, i. e. the “efficient cause” of the chick, or that which puts the egg in motion, and converts it into a chick. And let C be the chick, or “final cause,” for the sake of which both the egg and that which fecundates the egg exist, the actual chick, namely, or “reason” why the chick is.
Now we take for granted, as demonstrated by Aristotle,[398]that every prime mover is “combined with” that which is moved by it. And these things are more particularly said by him to be “together” which are generated or produced at the same moment of time: thus that which moves and that which is moved are actually together, and where one is there the other is also; for it is evident that when the effect is present the cause must be so too.
Whenever, then, A (i. e. the fecundated egg) is actually in being, B (i. e. the internal moving and “efficient” or fecundating cause) is also actually in being. But when B is actually in being, C also (i. e. the immaterial “form” of the chick) must, at least in some sort, be existing too. For B is the internal efficient cause of the chick, that, namely, which alters A (the egg) into C (the “reason” why the chick is). Since, then, everything which moves coexists with that which is moved by it, and every cause with its effect, it follows that C coexists with B; for the “final cause,” both in nature and art, is primary to all other causes, since it moves, and is not itself moved; but the “efficient” moves, because it is impelled by the “final cause.” There inheres, in some way or other, in every “efficient cause” a ratio finis (a final cause), and by this the efficient, co-operating with Providence, is moved.
The authority of Aristotle is clearly on my side: “That,” he says,[399]“appears to hold the chief place among natural causes which we signify under this expression, ‘cujus gratiâ’—for whose sake. For this is the ‘reason;’ but the ‘reason’ is the chief thing, as well in artificial as in natural subjects. For when a physician explains what health is, either by definition or description, or a workman a house, he is accustomed to givethe reasons and causes of what he does, and adds why he does it; although that cause, ‘cujus gratiâ,’ and the reason ‘for the sake of the good and fair,’ are joined rather to the works of nature than to those of art.”
“The end,” he elsewhere says,[400]“is this ‘cujus gratiâ’ (for whose sake), as health is the thing for the sake of which we walk. For why does a man walk? We answer, for the sake of his health; and when we have thus said, we think we have given a ‘cause;’ and whatever else is further interposed, by means of another agent, is done for the sake of this end, as dieting, or purging, or drugs, or instruments, are all for the sake of health; for all these are for the sake of the end.” Again, “It is our business always to seek the primary cause of everything. For instance, a man builds a house because he is a builder, but he is a builder by reason of the art of building; this then (the art) is a prior cause; and so in all things.” Hence it is that he asserts[401]“that the cause which first moves, and in which the ‘reason’ and ‘form’ lie, is greater and more divine than the ‘material cause.’”
In all natural generation, therefore, both the “matter” out of which and the “efficient cause” by which (namely, A, the thing which is moved, and B, the thing moving) are alike for the sake of the animal begotten or to be begotten; for that which moves and is not itself moved, viz. C, is in (inest) both. For both those (viz. A and B) are at the same time capable of motion, and are moreover moved, viz. the thing fecundating, B, (which both moves and is moved) and the thing fecundated, A, the “matter,” viz. or ovum, which is moved and changed only. Wherefore if no moveable thing is actually moved, unless the thing which moves is present, so neither will “matter” be moved, nor the “efficient” effect anything, unless the first moving cause be in some way present; and this is the “form” or “species” which is without matter, and is the prime cause. “For the efficient and generating,” according to Aristotle,[402]“in so far as they are so, belong to that which is effected and generated.” The following syllogism, therefore, may be framed out of these first and necessary predicates:
Whenever B is actually in existence, C also is actually in existence (i. e. moving in some way).
Whenever A is actually in existence, B is also in actual existence.
Therefore whenever A is in actual existence, C is also in actual existence.
Natural and artificial generation take place after the same manner.[403]Both are instituted for the sake of something further, and by a kind of providence both direct themselves to a proposed end;—both too are first moved by some “form” conceived without matter, and are the products of this conception. The brain is the organ of one kind of conception (for in the soul, the organ of which is the brain, art, without the intervention of matter, is the “reason” or first cause of the work), the uterus or ovum of the other.
The “conception,” therefore, of the uterus or the ovum resembles, at least in some sort, the conception of the brain itself, and in a similar way does the “end” inhere in both. For the “species” or “form” of the chick is in the uterus or ovum without the intervention of matter, just as the “reason” of his work is in the artist, e. g. the “reason” of the house in the brain of the builder.
But since the phrase “to be in” is perhaps equivocal, and things are said to be coexistent in various senses, I affirm, further, and say, that the “species” and immaterial “form” of the future chick are, in some sort, the cause of the impregnation or fecundation of the uterus, because after intercourse no corporeal substance can be found within that organ.
But how this immaterial cause, this first principle, exists alike in the uterus and brain, or how the conceptions of the brain and uterus, answering to art and nature, resemble or differ from each other, and in what way the thing which fecundates (viz. the internal efficient cause whereby the animal is generated) exists alike in the male and his semen and in the woman and her uterus—in the egg also, the mixed work of both sexes—and wherein their differences consist, I shall subsequently attempt to explain when I treat generally of the generation of animals (as well of those creatures which are produced by metamorphosis, viz. insects, as of spontaneously generated beings, in whose ova or “primordia,” as in all other seeds, the “species” or immaterial “form” plainly dwells, the moving principle, as it were, of those things which are to be generated), and when I speak of the soul and its affections, and how art, memory, and experience are to be regarded as the conceptions of the brain alone.
[This account first appeared in the work of Dr. Bett, entitled: “De Ortu et Natura Sanguinis,” 8vo. London, 1669, the MS. having been presented to Bett by Mr. Michael Harvey, nephew of the author, with whom Bett informs us he was on terms of intimacy.—Ed.]
Thomas Parr, a poor countryman, born near Winnington, in the county of Salop, died on the 14th of November, in the year of grace 1635, after having lived one hundred and fifty-two years and nine months, and survived nine princes. This poor man, having been visited by the illustrious Earl of Arundel when he chanced to have business in these parts, (his lordship being moved to the visit by the fame of a thing so incredible,) was brought by him from the country to London; and, having been most kindly treated by the earl both on the journey and during a residence in his own house, was presented as a remarkable sight to his Majesty the King.
Having made an examination of the body of this aged individual, by command of his Majesty, several of whose principal physicians were present, the following particulars were noted:
The body was muscular, the chest hairy, and the hair on the fore-arms still black; the legs, however, were without hair, and smooth.
The organs of generation were healthy, the penis neither retracted nor extenuated, nor the scrotum filled with any serous infiltration, as happens so commonly among the decrepid; the testes, too, were sound and large; so that it seemed not improbable that the common report was true, viz. that he did public penance under a conviction for incontinence, after he had passed his hundredth year; and his wife, whom he hadmarried as a widow in his hundred-and-twentieth year, did not deny that he had intercourse with her after the manner of other husbands with their wives, nor until about twelve years back had he ceased to embrace her frequently.
The chest was broad and ample; the lungs, nowise fungous, adhered, especially on the right side, by fibrous bands to the ribs. They were much loaded with blood, as we find them in cases of peripneumony, so that until the blood was squeezed out they looked rather blackish. Shortly before his death I had observed that the face was livid, and he suffered from difficult breathing and orthopnœa. This was the reason why the axillæ and chest continued to retain their heat long after his death: this and other signs that present themselves in cases of death from suffocation were observed in the body.
We judged, indeed, that he had died suffocated, through inability to breathe, and this view was confirmed by all the physicians present, and reported to the King. When the blood was expressed, and the lungs were wiped, their substance was beheld of a white and almost milky hue.
The heart was large, and thick, and fibrous, and contained a considerable quantity of adhering fat, both in its circumference and over its septum. The blood in the heart, of a black colour, was dilute, and scarcely coagulated; in the right ventricle alone some small clots were discovered.
In raising the sternum, the cartilages of the ribs were not found harder or converted into bone in any greater degree than they are in ordinary men; on the contrary, they were soft and flexible.
The intestines were perfectly sound, fleshy, and strong, and so was the stomach: the small intestines presented several constrictions, like rings, and were muscular. Whence it came that, by day or night, observing no rules or regular times for eating, he was ready to discuss any kind of eatable that was at hand; his ordinary diet consisting of sub-rancid cheese, and milk in every form, coarse and hard bread, and small drink, generally sour whey. On this sorry fare, but living in his home, free from care, did this poor man attain to such length of days. He even ate something about midnight shortly before his death.
The kidneys were bedded in fat, and in themselves sufficiently healthy; on their anterior aspects, however, they contained several small watery abscesses or serous collections, one of which, the size of a hen’s egg, containing a yellow fluid in a proper cyst, had made a rounded depression in the substance of the kidney. To this some were disposed to ascribe the suppression of urine under which the old man had laboured shortly before his death; whilst others, and with greater show of likelihood, ascribed it to the great regurgitation of serum upon the lungs.
There was no appearance of stone either in the kidneys or bladder.
The mesentery was loaded with fat, and the colon, with the omentum, which was likewise fat, was attached to the liver, near the fundus of the gall-bladder; in like manner the colon was adherent from this point posteriorly with the peritoneum.
The viscera were healthy; they only looked somewhat white externally, as they would have done had they been parboiled; internally they were (like the blood,) of the colour of dark gore.
The spleen was very small, scarcely equalling one of the kidneys in size.
All the internal parts, in a word, appeared so healthy, that had nothing happened to interfere with the old man’s habits of life, he might perhaps have escaped paying the debt due to nature for some little time longer.
The cause of death seemed fairly referrible to a sudden change in the non-naturals, the chief mischief being connected with the change of air, which through the whole course of life had been inhaled of perfect purity,—light, cool, and mobile, whereby the præcordia and lungs were more freely ventilated and cooled; but in this great advantage, in this grand cherisher of life this city is especially destitute; a city whose grand characteristic is an immense concourse of men and animals, and where ditches abound, and filth and offal lie scattered about, to say nothing of the smoke engendered by the general use of sulphureous coal as fuel, whereby the air is at all times rendered heavy, but much more so in the autumn than at any other season. Such an atmosphere could not have been found otherwise than insalubrious to one coming from the open, sunny and healthy region of Salop; it must have been especially so to one already aged and infirm.
And then for one hitherto used to live on food unvaried in kind, and very simple in its nature, to be set at a table loaded with variety of viands, and tempted not only to eat more than wont, but to partake of strong drink, it must needs fall out that the functions of all the natural organs would become deranged. Whence the stomach at length failing, and the excretions long retained, the work of concoction proceeding languidly, the liver getting loaded, the blood stagnating in the veins, the spirits frozen, the heart, the source of life, oppressed, the lungs infarcted, and made impervious to the ambient air, the general habit rendered more compact, so that it could no longer exhale or perspire—no wonder that the soul, little content with such a prison, took its flight.
The brain was healthy, very firm and hard to the touch; hence, shortly before his death, although he had been blind for twenty years, he heard extremely well, understood all that was said to him, answered immediately to questions, and had perfect apprehension of any matter in hand; he was also accustomed to walk about, slightly supported between two persons. His memory, however, was greatly impaired, so that he scarcely recollected anything of what had happened to him when he was a young man, nothing of public incidents, or of the kings or nobles who had made a figure, or of the wars or troubles of his earlier life, or of the manners of society, or of the prices of things—in a word, of any of the ordinary incidents which men are wont to retain in their memories. He only recollected the events of the last few years. Nevertheless, he was accustomed, even in his hundred and thirtieth year, to engage lustily in every kind of agricultural labour, whereby he earned his bread, and he had even then the strength required to thrash the corn.
To Caspar Hofmann, M.D. Published at Nurenberg, in the ‘Spicilegium Illustrium Epistolarum ad Casp. Hofmannum.’
Youropinion of me, my most learned Hofmann, so candidly given, and of the motion and circulation of the blood, is extremely gratifying to me; and I rejoice that I have been permitted to see and to converse with a man so learned as yourself, whose friendship I as readily embrace as I cordially return it. But I find that you have been pleased first elaborately to inculpate me, and then to make me pay the penalty, as having seemed to you “to have impeached and condemned Nature of folly and error; and to have imputed to her the character of a most clumsy and inefficient artificer, in suffering the blood to become recrudescent, and making it return again and again to the heart in order to be reconcocted, to grow effete as often in the general system; thus uselessly spoiling the perfectly-made blood, merely to find her in something to do.” But where or when anything of the kind was ever said, or even imagined by me—by me, who, on the contrary, have never lost an opportunity of expressing my admiration of the wisdom and aptness and industry of Nature,—as you do not say, I am not a little disturbed to find such things charged upon me by a man of sober judgment like yourself. In my printed book, I do, indeed, assert that the blood is incessantly moving out from the heart by the arteries to the general system, and returning from thisby the veins back to the heart, and with such an ebb and flow, in such mass and quantity that it must necessarily move in some way in a circuit. But if you will be kind enough to refer to my eighth and ninth chapters you will find it stated in so many words that I have purposely omitted to speak of the concoction of the blood, and of the causes of this motion and circulation, especially of the final cause. So much I have been anxious to say, that I might purge myself in the eyes of a learned and much respected man,—that I might feel absolved of the infamy of meriting such censure. And I beg you to observe, my learned, my impartial friend, if you would see with your own eyes the things I affirm in respect of the circulation,—and this is the course which most beseems an anatomist,—that I engage to comply with your wishes, whenever a fit opportunity is afforded; but if you either decline this, or care not by dissection to investigate the subject for yourself, let me beseech you, I say, not to vilipend the industry of others, nor charge it to them as a crime; do not derogate from the faith of an honest man, not altogether foolish nor insane, who has had experience in such matters for a long series of years.
Farewell, and beware! and act by me, as I have done by you; for what you have written I receive as uttered in all candour and kindness. Be sure, in writing to me in return, that you are animated by the same sentiments.
Nürnberg, May 20th, 1636.
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 justcome 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 on 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 theperforation 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[404]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 Siegel, 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 scrupleson 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 mouthsmutually 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 herewhich 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 thejudgment 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 lovingWilliam Harvey.
Written in London, this 26th of March, 1651.