Chapter XXXVI: Introduction (11)

From what has now been said, then, it appears that the blood is the first engendered part, whence the living principle in the first instance gleams forth, and from which the first animated particle of the embryo is formed; that it is the source and origin of all other parts, both similar and dissimilar, which thence obtain their vital heat and become subservient to it in its duties. But the heart is contrived for the sole purpose of ministering between the veins and the arteries--of receiving blood from the veins, and, by its ceaseless contractions, of propelling it to all parts of the body through the arteries.

This fact is made particularly striking, when we find that neither is there a heart found in every animal, neither does it necessarily and in every instance pulsate at all times where it is encountered; the blood, however, or a fluid which stands in lieu of it, is never wanting.

EXERCISE THE FIFTY-SECOND.

_Of the blood as prime element in the body._

It is unquestionable, then, and obvious to sense, that the blood is the first formed, and therefore the genital part of the embryo, and that it has all the attributes which have been ascribed to it in the preceding exercise. It is both the author and preserver of the body; it is the principal element moreover, and that in which the vital principle (anima) has its dwelling-place. Because, as already said, before there is any particle of the body obvious to sight, the blood is already extant, has already increased in quantity, “and palpitates within the veins,” as Aristotle expresses it,[276] “being moved hither and thither, and being the only humour that is distributed to every part of the animal body. The blood, moreover, is that alone which lives and is possessed of heat whilst life continues.”

And further, from its various motions in acceleration or retardation, in turbulence and strength, or debility, it is manifest that the blood perceives things that tend to injure by irritating, or to benefit by cherishing it. We therefore conclude that the blood lives of itself, and supplies its own nourishment; and that it depends in nowise upon any other part of the body, which is either prior to itself or of greater excellence and worth. On the contrary, the whole body, as posthumous to it, as added and appended as it were to it, depends on the blood, though this is not the place to prove the fact; I shall only say, with Aristotle,[277] that “The nature of the blood is the undoubted cause wherefore many things happen among animals, both as regards their tempers and their capacities.” To the blood, therefore, we may refer as the cause not only of life in general,--inasmuch as there is no other inherent or influxive heat that may be the immediate instrument of the living principle except the blood,--but also of longer or shorter life, of sleep and watching, of genius or aptitude, strength, &c. “For through its tenuity and purity,” says Aristotle in the same place, “animals are made wiser and have more noble senses; and in like manner they are more timid and courageous, or passionate and furious, as their blood is more dilute, or replete with dense fibres.”

Nor is the blood the author of life only, but, according to its diversities, the cause of health and disease likewise: so that poisons, which come from without, such as poisoned wounds, unless they infect the blood, occasion no mischief. Life and death, therefore, flow for us from the same spring. “If the blood becomes too diffluent,” says Aristotle,[278] “we fall sick; for it sometimes resolves itself into such a sanguinolent serum, that the body is covered with a bloody sweat; and if there be too great a loss of blood, life is gone.” And, indeed, not only do the parts of the body at all times become torpid when blood is lost, but if the loss be excessive, the animal necessarily dies. I do not think it requisite to quote any particular experiment in confirmation of these views: the whole subject would require to be treated specially.

The admirable circulation of the blood originally discovered by me, I have lived to see admitted by almost all; nor has aught as yet been urged against it by any one which has seemed greatly to require an answer. Wherefore I imagine that I shall perform a task not less new and useful than agreeable to philosophers and medical men, if I here briefly discourse of the causes and uses of the circulation, and expose other obscure matters respecting the blood; if I show, for instance, how much it concerns our welfare that by a wholesome and regulated diet we keep our blood pure and sweet. When I have accomplished this it will no longer, I trust, seem so improbable and absurd to any one as it did to Aristotle[279] in former times, that the blood should be viewed as the familiar divinity, as the soul itself of the body, which was the opinion of Critias and others, who maintained that the prime faculty of the living principle (anima) was to feel, and that this faculty inhered in the body in virtue of the nature of the blood. Thales, Diogenes, Heraclitus, Alcmæon, and others, held the blood to be the soul, because, by its nature, it had a faculty of motion.

Now that both sense and motion are in the blood is obvious from many indications, although Aristotle[280] denies the fact. And, indeed, when we see him, yielding to the force of truth, brought to admit that there is a vital principle even in the hypenemic egg; and in the spermatic fluid and blood a “certain divine something corresponding with the element of the stars,” and that it is vicarious of the Almighty Creator; and if the moderns be correct in their views when they say that the seminal fluid of animals emitted in coitu is alive, wherefore should we not, with like reason, affirm that there is a vital principle in the blood, and that when this is first ingested and nourished and moved, the vital spark is first struck and enkindled? Unquestionably the blood is that in which the vegetative and sensitive operations first proclaim themselves; that in which heat, the primary and immediate instrument of life, is innate; that which is the common bond between soul and body, and the vehicle by which life is conveyed into every particle of the organized being.

Besides, if it be matter of such difficulty to understand the spermatic fluid as we have found it, to fathom how through it the formation of the body is made to begin and proceed with such foresight, art, and divine intelligence, wherefore should we not, with equal propriety, admit an exalted nature in the blood, and think at least as highly of it as we have been led to do of the semen?--the rather, as this fluid is itself produced from the blood, as appears from the history of the egg; and the whole organized body not only derives its origin, as from a genital part, but even appears to owe its preservation to the blood.

We have, indeed, already said so much incidentally above, intending to speak on the subject more particularly at another time. Nor do I think that we are here to dispute whether it is strictly correct to speak of the blood as a _part_; some deny the propriety of such language, moved especially by the consideration that it is not sensible, and that it flows into all parts of the body to supply them with nourishment. For myself, however, I have discovered not a few things connected with the manner of generation which differ essentially from those motions which philosophers and medical writers generally either admit or reject. At this time I say no more on this point; but though I admit the blood to be without sensation, it does not follow that it should not form a portion, and even a very principal portion, of a body which is endowed with sensibility. For neither does the brain nor the spinal marrow, nor the crystalline or the vitreous humour of the eye, feel anything, though, by the common consent of all, philosophers and physicians alike, these are parts of the body. Aristotle placed the blood among the partes similares; Hippocrates, as the animal body according to him is made up of containing, contained, and impelling parts, of course reckoned the blood among the number of parts contained.

But we shall have more to say on this topic when we treat of that wherein a part consists, and how many kinds of parts there are. Meantime, I cannot be silent on the remarkable fact, that the heart itself, this most distinguished member in the body, appears to be insensible.

A young nobleman, eldest son of the Viscount Montgomery, when a child, had a severe fall, attended with fracture of the ribs of the left side. The consequence of this was a suppurating abscess, which went on discharging abundantly for a long time, from an immense gap in his side; this I had from himself and other credible persons who were witnesses. Between the 18th and 19th years of his age, this young nobleman, having travelled through France and Italy, came to London, having at this time a very large open cavity in his side, through which the lungs, as it was believed, could both be seen and touched. When this circumstance was told as something miraculous to his Serene Majesty King Charles, he straightway sent me to wait on the young man, that I might ascertain the true state of the case. And what did I find? A young man, well grown, of good complexion, and apparently possessed of an excellent constitution, so that I thought the whole story must be a fable. Having saluted him according to custom, however, and informed him of the king’s expressed desire that I should wait upon him, he immediately showed me everything, and laid open his left side for my inspection, by removing a plate which he wore there by way of defence against accidental blows and other external injuries. I found a large open space in the chest, into which I could readily introduce three of my fingers and my thumb; which done, I straightway perceived a certain protuberant fleshy part, affected with an alternating extrusive and intrusive movement; this part I touched gently. Amazed with the novelty of such a state, I examined everything again and again, and when I had satisfied myself, I saw that it was a case of old and extensive ulcer, beyond the reach of art, but brought by a miracle to a kind of cure, the interior being invested with a membrane, and the edges protected with a tough skin. But the fleshy part, (which I at first sight took for a mass of granulations, and others had always regarded as a portion of the lung,) from its pulsating motions and the rhythm they observed with the pulse,--when the fingers of one of my hands were applied to it, those of the other to the artery at the wrist--as well as from their discordance with the respiratory movements, I saw was no portion of the lung that I was handling, but the apex of the heart! covered over with a layer of fungous flesh by way of external defence, as commonly happens in old foul ulcers. The servant of this young man was in the habit daily of cleansing the cavity from its accumulated sordes by means of injections of tepid water; after which the plate was applied, and, with this in its place, the young man felt adequate to any exercise or expedition, and, in short, he led a pleasant life in perfect safety.

Instead of a verbal answer, therefore, I carried the young man himself to the king, that his majesty might with his own eyes behold this wonderful case: that, in a man alive and well, he might, without detriment to the individual, observe the movement of the heart, and, with his proper hand even touch the ventricles as they contracted. And his most excellent majesty, as well as myself, acknowledged that the heart was without the sense of touch; for the youth never knew when we touched his heart, except by the sight or the sensation he had through the external integument.

We also particularly observed the movements of the heart, viz.: that in the diastole it was retracted and withdrawn; whilst in the systole it emerged and protruded; and the systole of the heart took place at the moment the diastole or pulse in the wrist was perceived; to conclude, the heart struck the walls of the chest, and became prominent at the time it bounded upwards and underwent contraction on itself.

Neither is this the place for taking up that other controversy; to wit, whether the blood alone serves for the nutrition of the body? Aristotle in several places contends that the blood is the ultimate aliment of the body, and in this view he is supported by the whole body of physicians. But many things of difficult interpretation, and that hang but indifferently together, follow from this opinion of theirs. For when the medical writers speak of the blood in their physiological disquisitions, and teach that the above is its sole use and end, viz.: to supply nourishment to the body, they proceed to compose it of four humours, or juices, adducing arguments for such a view from the combinations of the four primary qualities; and then they assert that the mass of the blood is made up of the two kinds of bile, the yellow and the black, of pituita, and the blood properly so called. And thus they arrive at their four humours, of which the pituita is held to be cold and moist; the black bile cold and dry; the yellow bile hot and dry; and the blood hot and moist. Further, of each of these several kinds, they maintain that some are nutritious, and compose the whole of the body; others, again, they say are excrementitious. Still further, they suppose that the blood proper is composed of the nutritious or heterogeneous portions; but the constitution of the mass is such, that the pituita is a cruder matter, which the more powerful native heat can convert into perfect blood. They deny, however, that the bile can by any means be thus transformed into blood; although the blood, they say, is readily changed into bile, an event which they conceive takes place in melancholic diseases, through an excess of the concocting heat.

Now, if all this were true, and there be no retrogressive movement, viz. from black bile to bile, from bile to blood, they would be brought to the dilemma of having to admit that all the juices were present for the production of black bile, and that this was a principal and most highly concocted nutriment. It would further be imperative on them to recognize a kind of twofold blood, viz. one consisting of the entire mass of fluid contained in the veins, and composed of the four humours aforesaid; and another consisting of the purer, more fluid and spirituous portion, the fluid, which in the stricter sense they call blood, which some of them contend is contained in the arteries apart from the rest, and which they then depute upon sundry special offices. On their own showing, therefore, the pure blood is no aliment for the body, but a certain mixed fluid, or rather black bile, to which the rest of the humours tend.

Aristotle,[281] too, although he thought that the blood existed as a means of nourishing the body, still believed that it was composed as it were of several portions, viz. of a thicker and black portion which subsides to the bottom of the basin when the blood coagulates, and this portion he held to be of an inferior nature;[282] “for the blood,” he says, “if it be entire, is of a red colour and sweet taste; but if vitiated either by nature or disease, it is blacker.” He also will have it fibrous in part or partly composed of fibres, which being removed, he continues,[283] the blood neither sets nor becomes any thicker. He farther admitted a sanies in the blood: “Sanies is unconcocted blood, or blood not yet completely concocted, or which is as yet dilute like serum.” And this part, he says, is of a colder nature. The fibrous he believed to be the earthy portion of the blood.

According to the view of the Stagirite, therefore, the blood of different animals differs in several ways; in one it is more serous and thinner, a kind of ichor or sanies, as in insects, and the colder and less perfect animals; in another it is thicker, more fibrous, and earthy, as in the wild boar, bull, ass, &c. In some where the constitution is distempered, the blood is of a blacker hue; in others it is bright, pure, and florid, as in birds, and the human subject especially.

Whence, it appears, that in the opinion of the physicians, as well as of Aristotle, the blood consists of several parts, in some sort of the same description, according to the views of each. Medical men, indeed, only pay attention to human blood, taken in phlebotomy and contained in cups and coagulated. But Aristotle took a view of the blood of animals generally, or of the fluid which is analogous to it. And I, omitting all points of controversy, and passing by any discussion of the inconveniences that wait upon the opinions of writers in general, shall here touch lightly upon the points that all are agreed in, that can be apprehended by the senses, and that pertain more especially to our subject; intending, however, to treat of everything at length elsewhere.

Although the blood be, as I have said, a portion of the body,--the primogenial and principal part, indeed,--still, if it be considered in its mass, and as it presents itself in the veins, there is nothing to hinder us from believing that it contains and concocts nourishment within itself, which it applies to all the other parts of the body. With the matter so considered, we can understand how it should both nourish and be nourished, and how it should be both the matter and the efficient cause of the body, and have the natural constitution which Aristotle held necessary in a primogenial part, viz. that it should be partly of similar, partly of dissimilar constitution; for he says, “As it was requisite for the sake of sensation that there should be similar members in animal bodies, and as the faculty of perceiving, the faculty of moving, and the faculty of nourishing, are all contained in the same member (viz. the primogenate particle), it follows necessarily that this member, which originally contains inherent principles of the above kind, be extant both simply, that it may be capable of sensation of every description, and dissimilarly, that it may move and act. Wherefore, in the tribes that have blood, the heart is held to be such a member; in the bloodless tribes, however, it is proportional to their state.”

Now, if Aristotle understands by the heart that which first appears in the embryo of the chick in ovo, the blood, to wit, with its containing parts--the pulsating vesicles and veins, as one and the same organ, I conceive that he has expressed himself most accurately; for the blood, as it is seen in the egg and the vesicles, is partly similar and partly dissimilar. But if he understands the matter otherwise, what is seen in the egg sufficiently refutes him, inasmuch as the substance of the heart, considered independently of the blood--the ventricular cone--is engendered long afterwards, and continues white without any infusion of blood, until the heart has been fashioned into that form of organ by which the blood is distributed through the whole body. Nor indeed does the heart even then present itself with the structure of a similar and simple part, such as might become a primogenial part, but is seen to be fibrous, fleshy, or muscular, and indeed is obviously what Hippocrates styled it,--a muscle or instrument of motion. But the blood, as it is first perceived, and as it pulsates, included within its vesicle, has as manifestly the constitution which Aristotle held necessary in a principal part. For the blood, whilst it is naturally in the body, has everywhere apparently the same constitution; when extravasated, however, and deprived of its native heat, immediately, like any dissimilar compound, it separates into several parts.

Were the blood destined by nature, however, for the nourishment of the body only, it would have a more _similar_ constitution, like the chyle or the albumen of the egg; or at all events it would be truly one and a single body composed of the parts or juices indicated, like the other humours, such as bile of either kind, and pituita or phlegm, which retain the same form and character without the body, which they showed within their appropriate receptacles;--they undergo no such sudden change as the blood.

Wherefore, the qualities which Aristotle ascribed to a principal part are found associated in the blood; which as a natural body, existing heterogeneously or _dissimilarly_, is composed of these juices or parts; but as it lives and is a very principal animal part, consisting of these juices mingled together, it is an animated _similar_ part, composed of a body and a vital principle. When this living principle of the blood escapes, however, in consequence of the extinction of the native heat, the primary substance is forthwith corrupted and resolved into the parts of which it was formerly composed; first into cruor, afterwards with red and white parts, those of the red parts that are uppermost being more florid, those that are lowest being black. Of these parts, moreover, some are fibrous and tough, (and these are the uniting medium of the rest,) others ichorous and serous, in which the mass of coagulum is wont to swim. Into such a serum does the blood almost wholly resolve itself at last. But these parts have no existence severally in living blood; it is in that only which has become corrupted and is resolved by death that they are encountered.

Besides the constituents of the blood now indicated, there is yet another which is seen in the blood of the hotter and stronger animals, such as horses, oxen, and men also of ardent constitution. This is seen in blood drawn from the body as it coagulates, in the upper part of the red mass, and bears a perfect resemblance to hartshorn-jelly, or mucilage, or thick white of egg. The vulgar believe this matter to be the pituita; Aristotle designated it the crude and unconcocted portion of the blood.

I have observed that this part of the blood differs both from the others and from the mere serous portion in which the coagulated clot is wont to swim in the basin, and also from the urine which percolates through the kidneys from the blood. Neither is it to be regarded as any more crude or colder portion of the blood, but rather, as I conceive, as a more spiritual part; a conclusion to which I am moved by two motives: first, because it swims above the bright and florid portion--commonly thought to be the arterial blood--as if it were hotter and more highly charged with spirits, and takes possession of the highest place in the disintegration of the blood.

Secondly, in venesection, blood of this kind, which is mostly met with among men of warm temperament, strong and muscular, escapes in a longer stream and with greater force, as if pushed from a syringe, in the same way as we say that the spermatic fluid which is ejected vigorously and to a distance is both more fruitful and full of spirits.

That this mucaginous matter differs greatly from the ichorous or watery part of the blood, which, as if colder than the rest, subsides to the bottom of the basin, appears on two distinct grounds: for the watery and sanious portion is too crude and unconcocted ever to pass into purer and more perfect blood; and the thicker and more fibrous mucus swimming above the clot of the blood itself appears more concoct and better elaborated than this; and so in the resolution or separation of the blood it comes that the mucus occupies the upper place, the sanies the lower; the clot and red parts, however,--both those of a brighter and those of a darker colour,--occupy the middle space.

For it is certain that not only this part, but the whole blood, and indeed the flesh itself--as may be seen in criminals hung in chains--may be reduced to an ichorous sanies; that is to say, become resolved into the matters of which they were composed, like salt into the lixivium from which it had been obtained. In like manner, the blood taken away in any cachexy abounds in serum, and this to such an extent that occasionally scarce any clot is seen--the whole mass of blood forms one sanies. This is observed in leucophlegmatia, and is natural in bloodless animals.

Further, if you take away some blood shortly after a meal, before the second digestion has been completed and the serum has had time to descend by the kidneys, or at the commencement of an attack of intermittent fever, you will find it sanious, inconcoct, and abounding in serum. On the contrary, if you open a vein after fasting, or a copious discharge of urine or sweat, you will find the blood thick, as if without serum, and almost wholly condensed into clot.

And in the same way as in coagulating blood you find a little of the afore-mentioned supernatant mucus, so if you expose the sanies in question, separated from the clot, to a gentle heat over the fire, you will find it to be speedily changed into the mucus; an obvious indication that the water or sanies which separates from the blood in the basin, is perchance a certain element in the urine, but not the urine itself, although in colour and consistence it seems so in fact. The urine is not coagulated or condensed into a fibrous mucus, but rather into a lixivium; the watery or sanious portion of the urine, however, when lightly boiled, does occasionally run into a mucus that swims through the fluid; in the same way, as the mucus in question rendered recrudescent by corruption, liquefies and returns to the state of sanies.

So far at this time have I thought fit to produce these my own observations on this constituent of the blood, intending to speak more fully of it as well as of the other constituents cognizable by the senses, and admitted by Aristotle and the medical writers.

That I may not seem to wander too widely from my purpose, I would here have it understood that with Aristotle I receive the blood as a part of the living animal body, and not as it is commonly regarded in the light of mere gore. The Stagirite says:[284] “The blood is warm, in the sense in which we should understand warm water, did we designate that fluid by a simple name, not viewing it as heated. For heat belongs to its nature; just as whiteness is in the nature of a white man. But when the blood becomes hot through any affection or passion, it is not then hot of itself. The same thing must be said in regard to the qualities of dryness and moistness. Wherefore, in the nature of such things they are partly hot and partly moist; but separated, they congeal and become cold; and such is the blood.”

The blood consequently, as it is a living element of the body, is of a doubtful nature, and falls to be considered under two points of view. Materially and _per se_ it is called nourishment; but formally and in so far as it is endowed with heat and spirits, the immediate instruments of the vital principle, and even with vitality (anima), it is to be regarded as the familiar divinity and preserver of the body, as the generative first engendered and very principal part. And as the prolific egg contains within it the matter, instrument, and framer of the future pullet, and all physicians admit a mixture of the seminal fluids of the two sexes in the uterus during or immediately after intercourse as constituting the mixed cause, both material and efficient, of the fœtus; so might one with more propriety maintain that the blood was both the matter and preserver of the body, though not the sole aliment; because it is observed that in animals which die of hunger, and in men who perish of marasmus, a considerable quantity of blood is still found after death in the veins. And farther, in youthful subjects still growing, and in aged individuals declining and falling away, the relative quantity of blood continues the same, and is in the ratio of the flesh that is present, as if the blood were a part of the body, but not destined solely for its nourishment; for if it were so, no one would die of hunger so long as he had any blood left in his veins, just as the lamp is not extinguished whilst there is a drop of inflammable oil left in the cruise.

Now when I maintain that the living principle resides primarily and principally in the blood, I would not have it inferred from thence that I hold all bloodletting in discredit, as dangerous and injurious; or that I believe with the vulgar that in the same measure as blood is lost, is life abridged, because the sacred writings tell us that the life is in the blood; for daily experience satisfies us that bloodletting has a most salutary effect in many diseases, and is indeed the foremost among all the general remedial means: vitiated states and plethora of the blood, are causes of a whole host of diseases; and the timely evacuation of a certain quantity of the fluid frequently delivers patients from very dangerous diseases, and even from imminent death. In the same measure as blood is detracted, therefore, under certain circumstances, it may be said that life and health are added.

This indeed nature teaches, and physicians at all events propose to themselves to imitate nature; for copious critical discharges of blood from the nostrils, from hemorrhoids, and in the shape of the menstrual flux, often deliver us from very serious diseases. Young persons, therefore, who live fully and lead indolent lives, unless between their eighteenth and twentieth year they have a spontaneous hemorrhage from the nose or lower parts of the body, or have a vein opened, by which they are relieved of the load of blood that oppresses them, are apt to be seized with fever or smallpox, or they suffer from headache and other morbid symptoms of various degrees of severity and danger. Veterinary surgeons are in the habit of beginning the treatment of almost all the diseases of cattle with bloodletting.

EXERCISE THE FIFTY-THIRD.

_Of the inferences deducible from the course of the umbilical vessels in the egg._

We find the blood formed in the egg and embryo before any other part; and almost at the same moment appear its receptacles, the veins and the vesicula pulsans. Wherefore, if we regard the punctum saliens as the heart, and this along with the blood and the veins as constituting one and the same organ, conspicuous in the very commencement of the embryo, although we should admit that the proper substance of the heart was deposited subsequently, still we should be ready to admit with Aristotle that the heart (an organ made up of ventricles, auricles, vessels, and blood) was in truth the principal and primogenate part of the body, its own prime and essential element having been the blood, both in the order of nature and of genetic production.

The parts that in generation succeed the blood are the veins, for the blood is necessarily inclosed and contained in vessels; so that, as Aristotle observes, we find two meatus venales even from the very first, which canals, as we have shown in our history, afterwards constitute the umbilical vessels. It seems necessary, therefore, to say something here of the situation and course of these vessels.

In the first place, then, it is to be observed that all the arteries and veins have their origin from the heart, and are as it were appendices or parts added to the central organ. If therefore you carefully examine the embryo of the human subject, or one of the lower animals, and having divided the vena cava between the right auricle and the diaphragm, look into it upwards or towards the heart, you will perceive three foramina, the largest and most posterior of which tending to the spine is the vena cava; the anterior and lesser proceeds to the root and trunk of the umbilical vessels; the third and least of all enters the liver and is the origin and trunk of all the ramifications distributed to the convexity of that organ. Whence it clearly appears that the veins do by no means all proceed from the liver as their origin and commencement, but from the heart--unless indeed any one would be hardy enough to contend that a vessel proceeded from its branches, not the branches from the trunk of the vessel.

Moreover, as the vessels in question are distributed equally to the albumen and vitellus of the egg, not otherwise than as the roots of trees are connected with the ground, it is obvious that both of these substances must serve for the nutriment of the embryo, and that they are taken up and carried to it by these vessels. But this view is opposed to that of Aristotle, who everywhere maintains that the chick is formed from the albumen, and receives nourishment through the umbilicus alone. The albumen indeed is first consumed, and the yelk serves subsequently for food, supplying the place of the milk, which viviparous animals receive after their birth from their mothers. The food which nature provides for the young of viviparous tribes in the dug of the mother, she supplies in the yelk of the egg to the young of oviparous animals. Whence it happens, that when the albumen is almost wholly consumed, the vitellus still remains nearly entire in the egg, the chick being already perfect and complete; more than this, the yelk is still found in the abdomen of the chick long after its exclusion. Aristotle discovered some on the eighteenth day after the hatching; and I have myself seen a small quantity connected with the intestine at the end of six weeks from that epoch.

Nevertheless, from the yelk (which certainly does not decrease in the same ratio as the albumen whilst the chick is forming) that is taken into the abdomen of the chick, and from the distribution of vessels through its substance, the whole of these collecting into a single trunk which enters the porta of the liver, and doubtless earning that portion of yelk they have absorbed for more perfect elaboration in that viscus--these and other arguments of the like kind force me to say that I cannot do otherwise than admit with Aristotle that the yelk supplies food to the chick, and is analogous to milk.

The whole of the yelk, indeed, does not remain after the fœtus of the fowl is fully formed; for a certain portion of it has been liquefied on the very first appearance of the embryo, and receives branches of vessels no less than the albumen, by which, already prepared, it is carried as nourishment for the chick; still it is certain that the greater portion of the yelk remains after the disappearance of the albumen; that it is laid up in the abdomen of the chick when excluded, and, attracted or absorbed by the branches of the vena portæ, that it is finally carried to the liver.

It is manifest, therefore, that the chick when hatched, is nourished by the yelk in the first period of its independent existence. And as within the egg the embryo was nourished partly by the albumen, partly by the vitellus, but principally by the albumen, which is both present in larger quantity, and is more speedily consumed, so when the chick is hatched, and when all the nourishment that is taken must pass through the liver to undergo ulterior preparation, is it nourished partly by the vitellus and partly by chyle absorbed from the intestines, but principally by chyle, which the host of subdivisions of the mesenteric vessels seize upon, whilst there is but a single vessel from the porta distributed to the vitellus, and by and by but little of it remains. Nature, therefore, acts as does the nurse, who gradually habituates her infant to the food which is to take the place of her failing supply of milk. The pullet is thus gradually brought from food of more easy to food of more difficult digestion,--from yelk to chyle.

Wherefore there is every reason for what we perceive in connexion with the course of the veins in the egg. When the embryo first begins to be formed, they are distributed to the colliquament only, where the blood finds suitable nutriment and matter for the formation of the body; but by and by they extend into the thinner albumen, whence the chick, whilst it is yet in the state of gelatine or mucor, and resembles a maggot in form, derives its increase; the branches next extend into the thicker albumen, and then into the vitellus, that they may also contribute to the support of the fœtus, which, having at length arrived at maturity and been extruded, still preserves a portion of the yelk (or milk) within its abdomen, whereby it is maintained in part, in part by food selected and prepared for it by the mother, until it is able to look out for and to digest its own aliment. Thus does nature most wisely provide food through the whole round of generation, suited to the various strength of the digestive faculty in the future being. In the first period of the fœtal chick’s existence a more delicate food is prepared for it; more advanced, firmer and firmer food is supplied; and this is the reason, I apprehend, wherefore, the perfect egg consists not only of two portions of different colours, but is even provided with two kinds of albumen.

Now all this that we discover from actual experience of the matter accords with the opinion of Aristotle, where he says:[285] “The part which is hot is best adapted to give form to the limbs; that which is more earthy rather conduces to the constitution of the body and is more remote. Wherefore in eggs of two colours, the animal begins to be engendered from the white (for the beginning of animal life is in the hot), and derives its nourishment from the yellow. In the warmer animals, consequently, these parts are kept distinct from one another, viz. that from which the beginning is derived, and that whence the nourishment is obtained, and the one is white, the other yellow.”

From what has now been said it appears that the chick--and we shall show that it is not otherwise in all other animals--arises and is constituted as it were by a principle or soul inherent in the egg, and that in the same way the proper aliment is sought for and is supplied within the egg; whereby it comes that the chick is not dependent on its mother in the same way as plants are dependent on the ground; and it is not more correct to say that the chick is nourished by the blood of its mother, or that its heart beats, and that it lives through the spirits of its parent, than it would be to assert that it moved and felt through the organs, or grew and attained to adult age through the vital principle of its parent. It is manifest, on the contrary, and is allowed by all that the fœtal chick is nourished through its umbilical vessels; and that the vascular ramifications dispersed over the albumen and yelk imbibe nourishment from them and convey it to the fœtus. It is also admitted that the chick, when excluded from the shell, is supplied with nourishment, partly from yelk, partly from chyle, and that in either case the aliment passes by the same route, viz. by the vena portæ into the liver, the branches of this vessel effecting the transit.

It is therefore obvious, as I now say by the way, that the chyle by which all animals are nourished is brought by the mesenteric veins from the intestines; nor is there occasion to look for any new passage--by the lacteal vessels, to wit--or any route in adult animals other than that which we discover in the egg and chick. But we shall recur more fully in another place to the inconveniences of such an opinion as that referred to.

Lastly, from the structure of the umbilical vessels of the chick in ovo, some of which as stated in the history are veins, others arteries, it is legitimate to conclude that there is here a circular motion of the blood, such as we have already demonstrated in the animal body, in our book on the Motion of the Blood, and this for the sake of the nutrition and growth of the embryo, and because the umbilical veins are distributed to either fluid of the egg, that they may thence bring nutriment to the chick, and the arteries accompany the veins, that by their affluxive heat the alimentary matter may be duly concocted, liquefied, and made fit to answer the ends of nutrition.

And hence it happens that wherever veins--and here I would have it understood that both arteries and veins are intended--make their way into the albumen or vitellus, there these fluids look liquefied and different from the rest. For as soon as the branches of the veins shoot forth, the upper portion of the albumen in which they are implanted passing into colliquament, becomes transparent, whilst the lower portion, continuing thick and compact, is pushed into the inferior angle of the egg. In like manner a separation of the vitellus, as it seems into two portions, makes its appearance, the one being superior, and the other inferior, and these do not differ less from one another in character than melted differs from solid wax; now this division corresponds to the two parts which severally receive or do not receive blood-vessels.

Hence are we farther made more certain as to the commencement of animal generation and the prime inherent principle of the egg. For it is assuredly known that the cicatricula or spot on the yelk is the chief point in the egg, that to which all the rest are subordinate, and to which, if to any one thing more than another, is to be referred the cause, whatever it be, of fecundity in the egg:--certain it is that the generation of the embryo is begun within its precincts. Wherefore, as we have said, the first effect of incubation is to cause dilatation of the cicatricula, and the formation of the colliquament, in which the blood first flushes and veins are distributed, and where the effects of the native heat and the influence of the plastic power first show themselves. And then, the more widely the ramifications of these veins extend, in the same proportion do indications of the presence of the vital power and vegetative force appear. For every effect is a clear evidence of its efficient cause.

In a word I say,--from the cicatricula (in which the first trace of the native heat appears) proceeds the entire process of generation; from the heart the whole chick, and from the umbilical vessels the whole of the membranes called secundines that surround it. We therefore conclude that the parts of the embryo are severally subordinate, and that life is first derived from the heart.

EXERCISE THE FIFTY-FOURTH.

_Of the order of the parts in Generation from an egg, according to Fabricius._

Having already determined what part is to be esteemed the first, the blood, to wit, with its receptacles, the heart, veins, and arteries, the next thing we have to do is to speak of the rest of the parts of the body and of the order and manner of their generation.

Fabricius, in whose footsteps we have resolved to tread, in speaking of the generation of the chick in ovo, passes in review the actions which take place in the egg, and by the effect of which the parts are produced, discussing them _seriatim_, as if a clearer view were thence to be obtained of the order or sequence of generation. “There are three primary actions,” he says,[286] “which present themselves in the egg of the bird: 1st, the generation of the embryo; 2d, its growth; 3d, its nourishment. The first, or generation, is the proper action of the egg; the second and third, viz. growth and nutrition, go on for the major part without the egg, though they are begun and also perfectly performed within it. Now these actions, as they flow from three faculties, the generative, the nutritive, and auctive, so do three operations follow them. From generation all the parts of the chick result; from increase and nutrition, the growth and maintenance of its body. From studying the formation of the chick, we perceive that, under the influence of the generative faculty, the parts of the creature which formerly had no existence are produced: the matter of the egg is changed into the organized body of a chicken. But whilst any part or substance undergoes transmutation into another, it must needs be that its proper essence undergoes change, otherwise would it still remain as it was and unaltered; it must at the same time receive figure, position, and dimensions apt and convenient to its new nature; and indeed it is into these two states or circumstances that procreation of matter resolves itself, viz. transformation and conformation. The transformative and the formative faculties would therefore be the cause of these functions; and whilst one of them has produced every individual part of the chick, such as we see it, from the chalaza of the egg, the other has given it figure, articulations, and position, fitting it for its destined uses. The first, the transformative or alterative faculty, is entirely natural, and acts without all consciousness; and taking the hot, the cold, the moist, and the dry, it alters all through the substance of the chalaza, and in altering this substance changes it into the component parts of the chick, that is to say, into flesh, bones, cartilages, ligaments, veins, arteries, nerves, and all the other similar and simple parts of the animal, and these, through the proper and innate heat and spirit of the semen of the cock, out of the substance of the egg, that is to say, its chalaza; by altering and commuting, it engenders, creates, produces the proper substance of the chick, imparting at the same time to every substance its appropriate quality. The other, which is called the formative faculty, and which out of similar forms dissimilar parts,--namely, giving them elegance through figure, due dimensions, proper position, and congruous number--is much more noble than the former, is possessed of consummate sapience, and acts not naturally [or instinctively], but with election, and consciousness, and intelligence. For the formative faculty appears to have exact cognizance and foresight both of the future action and use of every part and organ. So much of the primary action of the egg, which is the generation of the chick, and to accomplish which both the semen of the cock as agent and fecundator, and the chalaza as matter are required. In the second place comes accretion or growth, which is accomplished by nutrition, whose faculties consist in attraction, retention, concoction, expulsion, and, finally, apposition, agglutination, and assimilation of food.”

But for my part I neither regard such a distribution of actions as correct, or useful, or convenient in this place. It is incorrect, because those actions which he would make distinct in kind and in time--for instance, that parts are first produced similar by the alterative or transformative faculty, to be afterwards fashioned and organized by the formative faculty, and finally made to grow by the auctive faculty--are never apparent in the generation of the chick; for the several parts are produced and distinguished and increased simultaneously. For although in the generation of those animals which are formed by metamorphosis, where from matter previously existing, and already adequate in quantity and duly prepared, all the parts are made distinct and conformed by transformation, as when a butterfly is formed from a caterpillar, a silkworm from a grub, still in generation by epigenesis the thing is very different, nor do the same processes go on as in ordinary nutrition, which is effected by the various actions of different parts working together to a common end, the food being here first assumed and retained, then digested, next distributed, and finally agglutinated. Nor is the _similar constitution_ the result of the transformative faculty, void of all foresight, as Fabricius imagined; but the organic comes from the formative faculty which proceeds with both consciousness and foresight. For generation and growth do not proceed without nutrition, nor nutrition or increase without generation; to nourish being in other terms to substitute for a certain quantity of matter lost as much matter of the same quality, flesh or nerve, in lieu of the matter, flesh or nerve, that has become effete. But what is this but to make or engender flesh or nerve? In like manner, growth cannot go on without generation, for all natural bodies are increased by the accession of new particles similar to those of which they formerly consisted, and this, taking place according to all their dimensions, they are distinguished as regards their parts, and are organized at the same time that they grow.

But to engender the chick is in truth nothing else than to fashion or make its several members and organs, which, although they are produced in a certain order, and some are postgenate to others,--the less important to the more principal organs--still, whilst the organs themselves are all distinguished, they are not engendered in such wise and order that the _similar_ parts are first formed, and the _organic_ parts afterwards compounded from them; or so that certain composing parts existed before other compounded parts which must be fashioned from them. For although the head of the chick and the rest of the body exist in the shape of a mucus or soft jelly, whence each of the parts is afterwards formed in sequence, and all are of _similar_ constitution in the first instance, still are they simultaneously produced and augmented in virtue of the same processes directed by the same agent; and in the same proportion as the matter resembling jelly increases, in like measure are the parts distinguished; for they are engendered, transmuted, and formed simultaneously; similar and dissimilar parts exist together, and from a small similar organ a larger one is produced. The thing, in short, is not otherwise than it is among vegetables, where from the straw proceeds the ear, the awns, and the grain--distinctly, severally, and yet together; or as trees put forth buds, from which are produced leaves, flowers, fruit, and finally seed.

All this we learn from an attentive study of the parts and processes of the incubated egg, inasmuch, as from things done, actions or operations are apprehended; from operations, faculties or forces, and from these we then infer the artificer, generator, or cause. In the generation of the pullet, consequently, the actions or faculties of the engendering cause enumerated by Fabricius, namely, the metamorphic and formative, do not differ in kind, or even in the relation of sequence, as that one is first and the other second, but, as Aristotle is wont to say, are one and the same in reason; not as happens with reference to the actions of the nutritive faculty,--attraction, concoction, distribution and apposition, to wit,--which all come into play in several places at several times. Were this not so, the engendering cause itself would be forced to make use of various instruments in order to accomplish its various operations.