But experience teaches us that all this is very different in fact, and that the bones are rather among the last parts to beformed. The bones of the extremities and skull, and the teeth, do not arise any sooner than the brain, the muscles, and the other fleshy parts: in new-born fœtuses, perfect in other respects, the place of the bones is supplied by mere membranes or cartilages, which are only subsequently and in the lapse of time converted into bones; a circumstance which sufficiently appears in the crania of new-born infants, and in the state of their ribs and articulations.
And although it be true that the first rudiments of the body are seen in the guise of a recurved keel, still this is a soft mucous and jelly-like substance, which has no affinity in nature, structure, or office to bone; and although certain globules depend from thence, the destined rudiments of the head, still these contain no solid matter, but are mere vesicles full of limpid water, which are afterwards formed into the brain, cerebellum, and eyes, which are all subsequently surrounded by the skull, at a period, however, when the beak and nails have already acquired consistency and hardness.
This view of Fabricius is therefore both imperfect and incorrect; inasmuch as he does not think of what nature performs in fact in the work of generation, so much as of what in his opinion she ought to do, betrayed into this by his comparison with the edifice reared by art. As if nature had imitated art, and not rather art nature!—mindful of which he himself says afterwards:[288]“It were better to say that art learned of nature, and was an imitator of her doings; for, as Galen everywhere reminds us, nature is both older and displays greater wisdom in her works than art.”
And then when we admit that the bones are the foundation of the whole body, without which it could neither support itself nor perform any movement, it is still sufficient if they arise simultaneously with the parts that are attached to them. And indeed the things that are to be supported not yet existing, the supports would be established in vain. Nature, however, does nothing in vain; nor does she form parts before there is a use for them. But animals receive their organs as soon as the offices of these are required. The first basis of Fabricius, therefore, is distinctly overthrown by his own observations on the egg, and the comparison drawn by Galen.
He appears to have come nearer the truth where he says:[289]“The other basis of the parts to be formed first or last is obtained from nature, that is, from the vital principle by which the animal body is ruled and directed. If there be two grades of this principle, the vegetative and animal, the vegetative must be held prior in point of nature and time, inasmuch as it is common to plants and animals; and assuredly the organs officiating in the vegetative office will be engendered and formed before those that belong to the sensitive and motive principle, especially to the chief organs which are in immediate relationship with the governing principle. Now these organs are two in especial—the liver and the heart: the liver as seat of concupiscence, of the vegetative or nutritive faculty; the heart, as the organ whose heat maintains and perfects the vegetative and every other faculty, and in this way has most intimate connexions and relations with the vegetative force. Whence, if after the third day you see the heart palpitating in the point where the chick is engendered, as Aristotle bears witness to the fact that you can, you will not be surprised but rather be disposed to admit that the heart belongs to the vegetative degree and exists for its sake. It is also consonant with reason that the liver should be engendered simultaneously with the heart, but should lie perdue or hidden, as it does not pulsate. And Aristotle himself admits that the heart and liver exist in the animal body for similar reasons; so that where there is a heart there also is a liver discovered. If the heart and liver be the parts first produced, then, it is also fair to suppose that the other organs subserving these two should be engendered in the same manner,—the lungs which exist for the sake of the heart; and, for the sake of the liver, almost all the viscera which present themselves in the abdomen.”
Still is all this very different from the sequence we witness in the egg. Nor is it true that the liver is engendered simultaneously with the heart; nor does the salve avail with which he would cover that infirmity where he says that the liver is concealed because it does not palpitate; for the eyes and vena cava and carina are all conspicuous enough from the commencement, although none of them palpitate. How come the liver and lungs, if they be then extant, to be visible without any palpitation? And then Fabricius himself has indicated aminute point situated in the centre of his figure of the chick of the fourth day, without stating, however, that it had any pulsation; and this he did not perceive to be the heart, but rather believed it to be the rudiment of the body. It is certain, therefore, that Fabricius spoke only from conjecture and preconceived opinion of the origin of the liver; even in the same way as others have done, Aldrovandus and Parisanus among the number, who, lighting upon two points, and perceiving that they did not pulsate simultaneously, straightway held that one was the heart, the other the liver. As if the liver ever pulsated, and these two points were aught but the two pulsating vesicles replying to each other by alternate contractions, in the way and manner we have indicated in our history!
Fabricius, therefore, is either deceived or deceives, when he says, “In the first stage of the production of the chick, the liver, heart, veins, arteries, lungs, and all the organs contained in the cavity of the abdomen, are engendered together; and in like manner are the carina, in other words, the head with the eyes and entire vertebral column and thorax engendered.” For the heart, veins, and arteries are perfectly distinguished some time before the carina; the carina, again, is seen before the eyes; the eyes, beak, and sides before the organs contained in the cavity of the abdomen; the stomach and intestines before the liver or lungs; and there are still other particulars connected with the order of production of the parts in generation, of which we shall speak by and by.
He is also mistaken when he would have the vegetative portion of the vital principle prior in nature and time to the sensitive and motive element. For that which is prior in nature is mostly posterior in the order of generation. In point of time, indeed, the vegetative principle is prior; because without it the sensitive principle cannot exist: an act—if the act of an organic body—cannot take place without organs; and the sensitive and motive organs are the work of the vegetative principle; the sensitive soul before the existence of action, is like a triangle within a quadrangle. But nature intended that that which was primary and most noble should also be primary; wherefore the vegetative force is by nature posterior in point of order, as subordinate and ministrative to the sensitive and motive faculties.
Of the order of the parts according to Aristotle.
The following appear to be Aristotle’s views of the order of generation:[290]“When conception takes place, the germ comports itself like a seed sown in the ground. For seeds likewise contain a first principle, which, existing in the beginning in potentia, by and by when it manifests itself, sends forth a stem and a root, by which aliment is taken up; for increase is indispensable. And so in a conception, in which all the parts of the body inhere in potentia, and the first principle exists in a state of special activity.”
This principle in the egg—the body analogous to the seed of a vegetable—we have called with Fabricius the spot or cicatricula, and have spoken of it as a very primary part of the egg, as that in which all the other parts inhere in potentia, and from whence each in its order afterwards arises. In this spot, in fact, is contained that—whatever it may be—by which the egg is made productive; and here is the first action of the formative faculty, the first effect of the vegetative heat revealed.
This spot, as we have said, dilates from the very commencement of the incubation, and expands in circles, in the centre of which a minute white speck is displayed, like the shining point in the pupil of the eye; and here anon is discovered the punctum saliens rubrum, with the ramifications of the sanguiferous vessels, and this as soon as the fluid, which we have called the colliquament, has been produced.
“Wherefore,” adds Aristotle,[291]“the heart is the first part perceived in fact; and this is in conformity not only with sense, but also with reason. For as that which is engendered is already disjunct and severed from both parents, and ought to rule and regulate itself like a son who comes of age and has his separate establishment, it must therefore possess a principle, an intrinsic principle, by which the order of the members maybe subsequently determined, and whatever is necessary to the constitution of a perfect animal arranged. For if this principle were at any time extrinsic, and entered into the body at a subsequent period, you would not only be in doubt as to the time at which it entered, but as every part is distinct, you would also see it as necessary that that should first exist from which the other parts derive both increase and motion.” The same writer elsewhere[292]asserts: “This principle is a portion of the whole, and not anything added, or included apart. For,” he proceeds, “the generation of the animal completed, does this principle perish, or does it continue? But nothing can be shown existing intrinsically which is not a part of the whole organized being, whether it be plant or animal; wherefore it would be absurd to maintain that the principle in question perished after the formation either of any one or of any number of parts; for what should form those that were not yet produced? Wherefore,” he continues further, “they say not well who with Democritus assert that the external parts of animals are those first seen, and then the internal parts, as if they were rearing an animal of wood and stone, for such a thing would include no principle within itself. But all animals have and hold a principle in their interior. Wherefore the heart is seen as the first distinct part in animals that have blood; for it is the origin of all the parts, whether similar or dissimilar; and the creature that begins to feel the necessity of nourishment, must already be possessed by the principle of an animal and a full-grown fœtus.”
From the above, it clearly appears that Aristotle recognizes a certain order and commencement in animal generation, namely, the heart, which he regards as the first produced and first vivified part of the animal, and, like a son set free from the tutelage of his parents, as self-sufficing and independent, whence not only does the order of the parts proceed, but as that by which the animal itself is maintained and preserved, receiving from it at once life and sustenance, and everything needful to the perfection of its being. For as Seneca says:[293]“In the semen is comprised the entire cause of the future man; and the unborn babe has written within it the law of a beard and ahoary head. For the whole body and the load of future years are already traced in delicate and obscure outlines in its constitution.”
We have already determined whether the heart were this primigenial part or not; in other words, whether Aristotle’s words refer to that part which, in the dissection of animals, is seen sooner than all the rest, the punctum saliens, to wit, with its vessels full of blood; and we have cordially assented to an answer in the affirmative. For I believe that the blood, together with its immediate instruments, the umbilical vessels, by which, as by roots, nutriment is attracted, and the pulsating vesicles, by which this nutriment is distributed, to maintain life and growth in every other part, are formed first and foremost of all. For as Aristotle[294]has said, it is the same matter by which a thing grows, and by which it is primarily constituted.
Many, however, err in supposing that different parts of the body require different kinds of matter for their nourishment. As if nutrition were nothing more than the selection and attraction of fit aliment; and in the several parts of the body to be nourished, no concoction, assimilation, apposition, and transmutation were required. This as we learn, was the opinion of Anaxagoras of old:
Who held the principles of things to beHomœomeric:—bone to be producedOf small and slender bones; the visceraOf small and slender viscera; the bloodOf numerous associate drops of blood.[295]
Who held the principles of things to beHomœomeric:—bone to be producedOf small and slender bones; the visceraOf small and slender viscera; the bloodOf numerous associate drops of blood.[295]
Who held the principles of things to beHomœomeric:—bone to be producedOf small and slender bones; the visceraOf small and slender viscera; the bloodOf numerous associate drops of blood.[295]
But Aristotle,[296]with the greatest propriety, observes: “Distinction of parts is not effected, as some think, by like being carried by its nature to like; for, besides innumerable difficulties belonging to this opinion in itself, it happens that each similar part is severally created; for example, the bones by themselves, the nerves, the flesh, &c.” But the nourishment of all parts is common and homogeneous, such as we see the albumen to be in the egg, not heterogeneous and composed of different parts. Wherefore all we have said of the matter from which parts are made, is to be stated of that by which they increase: all derive nourishment from that in which they exist in potentia, thoughnot in act. Precisely as from the same rain plants of every kind increase and grow; because the moisture which was a like power in reference to all, becomes actually like to each when it is changed into their substances severally: then does it acquire bitterness in rue, sharpness in mustard, sweetness in liquorice, and so on.
He explains, moreover, what parts are engendered before others, and assigns a reason which does not differ from the second basis of Fabricius. “The cause by which, and the cause of this cause, are different; one is first in generation, the other in essence;” by which we are to understand that the end is prior in nature and essence to that which happens for the sake of the end; but that which happens for the sake of the end must be prior in generation. And on this ground Fabricius rightly infers that all those parts which minister to the vegetative principle, are engendered before those that serve the sensitive principle, inasmuch as the former is subordinate to the latter.
He subsequently adds the differences of those parts which are made for some special purpose: some parts, for example, are instituted for a purpose by nature, because this purpose ensues; and others because they are instruments which the purpose employs. The former he designates genitalia, the latter instrumenta. For the end or purpose, he says, in some cases, is posterior, in others prior to that which is its cause. For both the generator and the instruments it uses must exist anteriorly to that which is engendered by or from them. The parts serving the vegetative principle, therefore, are prior to the parts which are the ministers of sense and motion. But the parts dedicated to motion and sensation are posterior to the motive and sensitive faculties, because they are the instruments which the motive and sensitive faculties employ. For it is a law of nature that no parts or instruments be produced before there be some use for them, and the faculty be extant which employs them. Thus there is neither any eye nor any motive organ engendered until the brain is produced, and the faculties preexist which are to see and to govern motion.
In like manner, as the pulsating vesicles serve as instruments for the motion of the blood, and the heart in its entire structure does the same, (as I have shown in the work on the Motion of the blood,) urging the blood in a ceaseless round through every part of the body, we see that the blood must exist before the heart, both in the order of generation and of nature and essence. For the blood uses the heart as an instrument, and moreover, when engendered it continues to nourish the organ by means of the coronary arteries, distributing heat, spirits, and life to it through their ramifications.
We shall have further occasion to show from an entire series of anatomical observations, how this rule of Aristotle in respect of the true priority of the parts is borne out. Meantime we shall see how he himself succeeds in duly inferring the causes of priority in conformity with his rule.
“After the prime part—viz. the heart—is engendered,” he says, “the internal parts are produced before the external ones, the superior before the inferior; for the lower parts exist for the sake of the superior, and that they may serve as instruments, after the manner of the seeds of vegetables, which produce roots sooner than branches.”
Nature, however, follows no such order in generation; nor is the instance quoted invariably applicable; for in beans, peas, and other leguminous seeds, in acorns, also, and in grain, it is easy to see that the stem shoots upwards and the root downwards from the same germ; and onions and other bulbous plants send off stalks before they strike root.
He then subjoins another cause of this order, viz.: “That as nature does nothing in vain or superfluously, it follows that she makes nothing either sooner or later than the use she has for it requires.” That is to say, those parts are first engendered whose use or function is first required; and some are begun at an earlier period because a longer time is requisite to bring them to perfection; and that so they may be in the same state of forwardness at birth as those that are more rapidly produced. Just as the cook, having to dress certain articles for supper, which by reason of their hardness are done with difficulty, or require gentle boiling for a great length of time, these he puts on the first, and only turns subsequently to those that are prepared more quickly and with less expenditure of heat; and further, as he makes ready the articles that are to come on in the first course first of all, and those that are to be presented in the second course afterwards; so also does naturein the generation of animals only proceed at a later period to the construction of the soft and moist and fleshy parts, as requiring but a short time for their concoction and formation, whilst the hard parts, such as the bones, as requiring ample evaporation and abundant drying, and their matter long remaining inconcoct, she proceeds to fashion almost from the very beginning. “And the same thing obtains in the brain,” he adds, “which, large in quantity and exceedingly moist at first, is by and by better concocted and condensed, so that the brain as well as the eye diminishes in size. The head is therefore very large at first, in comparison with the rest of the body, which it far surpasses because of the brain and the eyes, and the large quantity of moisture contained in them. These parts, nevertheless, are among the last to be perfected, for the brain acquires consistence with difficulty, and it is long before it is freed from cold and moisture in any animal, and especially in man. The sinciput, too, is consolidated the last, the bones here being quite soft when the infant sees the light.”
He gives another reason, viz. because the parts are formed of different kinds of matter: “Every more excellent part, the sharer in the highest principle is, farther, engendered from the most highly concocted, the purest and first nutriment; the other needful parts, produced for the sake of the former, from the worse and excrementitious remainder. For nature, like the sage head of a family, is wont to throw away nothing that may be turned to any useful purpose. But he still regulates his household so that the best food shall be given to his children, the more indifferent to his menials, the worst to the animals. As then, man’s growth being complete and mind having been superadded, (in other words, and, as I interpret the passage, adult man having acquired sense and prudence,) things are ordered in this way, so does nature at the period of production even compose the flesh and the other more sensitive parts of the purest matter. Of the excrementitious remainder she makes the bones, sinews, hair, nails, and other parts of the same constitution. And this is the reason why this is done last of all, when nature has an abundant supply of recrementitious material.” Our author then goes on to speak of “a twofold order of aliment:” “one for nutrition, another for growth;” “the nutritive is the one which supplies existence to the whole andto the parts; the augmentative, that which causes increase to the bulk.”
This is in accordance with what we find in the egg, where the albumen supplies a kind of purer aliment adapted to the nutrition of the embryo in its earlier stages, and the yelk affords the material for the growth of the chick and pullet. The thinner albumen, moreover, as we have seen, is used in fashioning the first and more noble parts; the thicker albumen and the yelk, again, are employed in nourishing and making these to grow, and further in forming the less important parts of the body. “For,” he says, “the sinews, too, are produced in the same way as the bones, and from the same material, viz.: the seminal and nutritive excrementitious matter. But the nails, hair, horns, beak, and spurs of birds, and all other things of the same description, are engendered of the adventitious and nutritive aliment, which is obtained both from the mother and from without.” And then he gives a reason why man, whilst other animals are endowed by nature with defensive and offensive arms, is born naked and defenceless, which is this: that whilst in the lower animals these parts are formed of remainders or excrements, man is compounded of a purer material, “which contains too small a quantity of inconcoct and earthy matter.”
Thus far have we followed Aristotle on the subject of ‘The Order in Generation,’ the whole of which seems to be referrible to one principle, viz.: the perfection of nature, which in her works does nothing in vain and has no short-comings, but still does that in the best manner which was best to be done. Hence in generation no part would either precede or follow, did she prefer producing them altogether, viz.: in circumstances where she acts freely and by election; for sometimes she works under compulsion, as it were, and beside her purpose, as when through deficiency or superabundance of material, or through some defect in her instruments, or is hindered of her ends by external injuries. And thus it occasionally happens that the final parts are formed before the instrumental parts,—understanding by final parts, those that use others as instruments.
And as some of the parts are genital, nature making use of them in the generation of other parts, as the means of removing obstacles the presence of which would interfere with the due progress of the work of reproduction, and others exist forother special ends; it therefore happens that for the disposition of material, and other requisites, some parts are variously engendered before others, some of them being begun earlier but completed at a later period, some being both begun and perfected at an earlier period, and others being begun together but perfected at different times subsequently. And then the same order is not observed in the generation of all animals, but this is variously altered; and in some there is nothing like succession, but all the parts are begun and perfected simultaneously, by metamorphosis, to wit, as has been already stated. Hence it follows, in fine, that the primogenate part must be of such a nature as to contain both the beginning and the end, and be that for whose sake all the rest is made, namely, the living principle, or soul, and that which is the potential and genital cause of this, the heart, or in our view the blood, which we regard as the prime seat of the soul, as the source and perennial centre of life, as the generative heat, and indeed as the inherent heat; in a word, the heart is the first efficient of the whole of the instrumental parts that are produced for the ends of the soul, and used by it as instruments. The heart, according to Aristotle, I say, is that for which all the parts of animals are made, and it is at the same time that which is at once the origin and fashioner of them all.
Of the order of the parts in generation as it appears from observation.
That we may now propose our own views of the order of the parts in generation as we have gathered it from our observations, it appears that the whole business of generation in all animals may be divided into two periods, or connected with two structures: the ovum, i. e. the conception and seed, or that, whatever it be, which in spontaneous productions corresponds to the seed, whether with Fernelius it be called “the native celestial heat in the primogenial moisture,” or with Aristotle, “the vital heat included in moisture.” For the conception in viviparous animals, as we have said, is analogous tothe seed and fruit of plants; in the same way as it is to the egg of oviparous creatures; to worms in spontaneously engendered animals, or to certain vesicles fruitful by the vital warmth of their included moisture. In each and all of these the same things inhere which might with propriety lead to their being called seeds; they are all bodies, to wit, from which and by which, as previously existing matter, artificer and organ, the whole of an animal body is primarily engendered and produced.
The other structure is the embryo produced from the seed or conception. For both the matter and the moving and efficient cause, and the instruments needful to the operation, must necessarily precede operation of any and every kind.
We have already examined the structure of the egg. Now the embryo to which it gives birth, in so far as this can be made out by observation and dissection, particularly among the more perfect animals with [red] blood, appears to be perfected by four principal degrees or processes, which we reduce to as many orders, in harmony with the various epochs in generation; and we shall demonstrate that what transpires in the egg also takes place in every conception or seed.
The first process is that of the primogenial and genital part, viz. the blood with its receptacles, in other words, the heart and its vessels.
And this part is first engendered for two principal reasons: 1st, because it is the principal part which uses all the rest as instruments, and for whose sake the other parts are formed; and, 2d, because it is the prime genital part, the origin and author of the rest. The part, in a word, in which inhere both the principle whence motion is derived, and the end of that motion, is obviously father and sovereign.
In the generation of this first part, which in the egg is accomplished in the course of the fourth day, although I have not been able to observe any order or sequence, inasmuch as the whole of its elements,—the blood, the vessels, and the pulsating vesicles—appear simultaneously, I have nevertheless imagined, as I have said, that the blood exists before the pulse, because, according to nature’s laws, it must be antecedent to its receptacles. For the substance and structure of the heart, namely, the conical mass with its auricles and ventricles, as they are produced longsubsequently along with the other viscera, so must they be referred to the same class of parts as these, namely, the third.
In the production of the circulating system the veins are sooner seen than the arteries; such at least is our conclusion.
The second process, which begins after the fourth day, is indicated by a certain concrescence, which I designate vermiculum—worm or maggot; for it has the life and obscure motions of a maggot; and as it concretes into a mucous matter, it divides into two parts, the larger and superior of which is seen to be conglobed, and divided, as it were, into thin vesicles,—the brain, the cerebellum, and the two eyes; the less, again, constituting the carina, arises over the vena cava and extends in the line of its direction.
In the genesis of the head, the eyes are first perceived; by and by a white point makes its appearance in the situation of the beak, and the slime drying around it, it becomes invested with a membrane.
The outline of the rest of the body follows about the same period. First, from the carina something like the sides of a ship are seen to arise; the parts having an uniform consistence in the beginning, but the ribs being afterwards prefigured by means of extremely fine white lines. The instruments of locomotion next arise—the legs and wings; and the carina and the extremities adnate to it are then distinguished into muscles, bones, and articulations.
These two rudiments of the head and trunk appear simultaneously, but as they grow and advance to perfection subsequently, the trunk increases and acquires its shape much more speedily than the head; so that this, which in the first instance exceeded the whole trunk in size, is now relatively much smaller. And the same thing occurs in regard to the human embryo.
The same disparity also takes place between the trunk and the extremities. In the human embryo, from the time when it is not longer than the nail of the little finger, till it is of the size of a frog or mouse, the arms are so short that the extremities of the fingers could not extend across the breast, and the legs are so short that were they reflected on the abdomen they would not reach the umbilicus.
The proportion of the body to the extremities in children after their birth continues excessive until they begin to standand run. Infants, therefore, resemble dwarfs in the beginning, and they creep about like quadrupeds, attempting progressive motion with the assistance of all their extremities; but they cannot stand erect until the length of the leg and thigh together exceeds the length of the rest of the body. And so it happens, that when they first attempt to walk, they move with the body prone, like the quadruped, and can scarcely rise so erect as the common dunghill fowl.
And so it happens that among adult men the long-legged—they who have longer legs, and especially longer thighs—are better walkers, runners, and leapers than square-built, compact men.
In this second process many actions of the formative faculty are observed following each other in regular order, (in the same way as we see one wheel moving another in automata, and other pieces of mechanism,) and all arising from the same mucaginous and similar matter. Not indeed in the manner that some natural philosophers would have it when they say, “that like is carried to its like.” We are rather to maintain that parts are moved, not changing their places, but remaining and undergoing change in hardness, softness, colour, &c., whence the diversities betweensimilarparts; those things appearingin actwhich were beforein power.[297]The extremities, spine, and rest of the body, namely, are formed, grow, and acquire outline and complexion together; the extremities, comprising bones, muscles, tendons, and cartilages, all of which on their first appearance were similar and homogeneous, become distinguished in their progress, and, connected together, compose organs, by whose mutual continuity the whole body is constituted. In like manner, the membrane growing around the head, the brain is composed, and the lustrous eyes receive their polish out of a perfectly limpid fluid.
That is to say, nature sustains and augments the several parts by the same nourishment with which she fashioned them at first, and not, as many opine, with any diversity of aliment and particles similar to each particular structure. As she is increasing the mucaginous mass or maggot, like a potter she first divides her material, and then indicates the head and trunkand extremities; like a painter, she first sketches the parts in outline, and then fills them in with colours; or like the shipbuilder, who first lays down his keel by way of foundation, and upon this raises the ribs and roof or deck: even as he builds his vessel does nature fashion the trunk of the body and add the extremities. And in this work she orders all the variety of similar parts—the bones, cartilages, membranes, muscles, tendons, nerves, &c.—from the same primary jelly or mucus. For thick filaments are produced in the first instance, and these by and by are brought to resemble cords; then they are rendered cartilaginous and spinous; and, lastly, they are hardened and concocted into bones. In the same way the thicker membrane which invests the brain is first cartilaginous and then bony, whilst the thinner membrane merely consolidates into the pericranium and integument. In similar order flesh and nerve from soft mucus are confirmed into muscle, tendon, and ligament; the brain and cerebellum are condensed out of a perfectly limpid water into a firm coagulum; for the brain of infants, before the bones of the head have closed, is soft and diffluent, and has no greater consistence than the curd of milk.
The third process is that of the viscera, the formation of which in the chick takes place after the trunk is cast in outline, or about the sixth or seventh day,—the liver, lungs, kidneys, cone and ventricles of the heart, and intestines, all become visible nearly at the same moment; they appear to arise from the veins, and to be connected with them in the same way as fungi grow upon the bark of trees. They are, as I have already said, gelatinous, white, and bloodless, until they take on their proper functions. The stomach and intestines are first discovered as white and tortuous filaments extending lengthwise through the abdomen; along with these the mouth appears, from which a continuous canal extends to the anus, and connects the superior with the inferior parts. The organs of generation likewise appear about the same time.
Up to this period all the viscera, the intestines, and the heart itself inclusive, are excluded from the cavities of the body and hang pendulous without, attached as it were to the veins. The trunk of the body presents itself, in fact, like a boat undecked or a house without a roof, the anterior walls of the thorax and abdomen not being yet extant to close these cavities.
But as soon as the sternum is fashioned the heart enters into the chest as into a dwelling which it had built and arranged for itself; and there, like the tutelary genius, it enters on the government of the surrounding mansion, which it inhabits with its ministering servants the lungs. The liver and stomach are by and by included within the hypochondria, and the intestines are finally surrounded by the abdominal parietes. And this is the reason wherefore without dissection the heart can no longer be seen pulsating in the hen’s egg after the tenth day of incubation.
About this epoch the point of the beak and the nails appear of a fine white colour; a quantity of chylous matter presents itself in the stomach; a little excrement is also observed in the intestine, and the liver being now begun, some greenish bile is perceived; facts from which it clearly appears that there is another digestion and preparation of nutriment going on besides that which takes place by the branches of the umbilical veins; and it is reasonable matter of doubt how the bile, the excrementitious matter of the second digestion, can be separated by the instrumentality of the liver from the other humours, when we see it produced at the same time as this organ.
In the order now indicated are the internal organs generated universally; in all the animals which I have dissected, particularly the more perfect ones, and man himself, I have found them produced in the same manner: in these, in the course of the second, third, and fourth month, the heart, liver, lungs, kidneys, spleen, and intestines present themselves inchoate and increasing, and all alike of the same white colour which belongs to the body at large. Wherefore these early days are not improperly spoken of as the days when the embryo isin the milk; for with the exception of the veins, particularly those of the umbilicus, everything is as it were spermatic in appearance.
I am of opinion that the umbilical arteries arise after the veins of the same name, because the arteries are scarcely to be discovered in the course of the first month, and take their rise from the branches that descend to either lower extremity. I do not believe, therefore, that they exist until that part of the body whence they proceed is formed. The umbilical veins, on the contrary, are conspicuous long before any part of the body is begun.
What I have now said I have derived from numerous dissections of human embryos of almost every size; for I have had them for inspection from the time they were like tadpoles, till they were seven or eight fingers’ breadth in length, and from thence onwards to the full time. I have examined them more particularly, however, through the second, third, and fourth months, in the course of which the greatest number of changes take place, and the order of development is seen with greatest clearness.
In the human embryo, then, of the age of two months, what we have spoken of as taking place in the “second process,” is observed to occur. For I rather think that during the first month there is scarcely anything of the conception in the uterus—at all events, I have never been able to discover anything. But the first month past, I have repeatedly seen conceptions thrown off, and similar to the one which Hippocrates mentions as having been voided by the female pipe-player, of the size of a pheasant’s or pigeon’s egg. Such conceptions resemble an egg without its shell; they are, namely, of an oval figure; the thicker membrane or chorion with which they are surrounded, however, is seen to be covered with a white mucor externally, particularly towards the larger end; internally it is smooth and shining, and is filled with limpid and sluggish water—it contains nothing else.
In the course of the second month I have frequently seen an ovum of this description, or somewhat larger, thrown off with the symptoms of abortion, viz. ichorous lochia; the ovum being sometimes entire, at other times burst, and covered with bloody coagula. Within it was smooth and slippery; it was covered with adhering blood without. Its form was that which I have just described. In some of these aborted ova, I have discovered embryos, in others I could find none. The embryo, when present, was of the length of the little finger-nail, and in shape like a little frog, save that the head was exceedingly large and the extremities very short, like a tadpole in the month of June, when it gets its extremities, loses its tail, and assumes the form of a frog. The whole substance was white, and so soft and mucilaginous, that unless immersed in clear water, it was impossible to handle it. The face was the same as that of the embryo of one of the lower animals—the dog or cat, forinstance, without lips, the mouth gaping, and extending from ear to ear.
Many women, whose conceptions, like the wind-eggs of fowls, are barren and without an embryo, miscarry in the third month.
I have occasionally examined aborted ova of this age, of the size of a goose’s egg, which contained embryos distinct in all their parts, but misshapen. The head, eyes, and extremities were distinct, but the muscles were indistinct; there were no bones, but certain white lines in their situations, and as it seemed, soft cartilages. The substance of the heart was extremely white, and consisted of two ventricles of like size and thickness of walls, forming a cone with a double apex, which might be compared to a small twin-kernel nut. The liver was very small and of the general white colour. Through the whole of this time, i. e. during the first three months, there is scarcely any appearance of a placenta or uterine cake.
In every conception of this description I have seen, I have always found a surrounding membrane containing a large quantity of watery fluid, between which and the body of the embryo, suspended by its middle by means of a long and twisted umbilical cord, there is such disproportion, that it is impossible to regard this liquid as either sweat or urine; it seems far more probable that like the colliquament in the hen’s egg, it is a fluid destined by nature for the nourishment of the fœtus. Nor was there any indication to be discovered of these conceptions or ova having been connected with the uterus; there was only on the external surface of their larger extremity a greater appearance of thickening and wrinkling, as if the rudiments of the future placenta had existed there.
These conceptions, therefore, appear to me in the light of ova, which are merely cherished within the uterus, and, like the egg in the uterus of the fowl, grow by their own inherent powers.
In the fourth month, however, it is wonderful to find what rapid strides the fœtus has made: from the length of the thumb it has now grown to be a span long. All the members, too, are distinct and are tinged with blood; the bones and muscles can be distinguished; there are vestiges of the nails, and the fœtus now begins to move lustily. The head, however, is excessively large; the face without lips, cheeks, and nose; the gape of themouth is enormous, and the tongue lies in its middle; the eyes are small, without lids to cover them; the middle integument of the regions of the forehead and sinciput is not yet cartilaginous, far less bony; but the occiput is somewhat firm and in some sort cartilaginous, indicating that the skull already begins to acquire solidity.
The organs of generation have now made their appearance, but the testes are contained within the abdomen, in the situation of the female uterus, the scrotum still remaining empty. The female organs are yet imperfect, and the uterus with its tubes resembles the two-horned uterus of the lamb.
The placenta, of larger size, and now attached to the uterus, comprises nearly one half of the entire conception, and presented itself to my eye as a fleshy or fungous excrescence of the womb, so firmly was its gibbous portion connected all around with the uterine walls, which had now grown to greater thickness. The branches of the umbilical vessels struck into the placenta like the roots of a tree into the ground, and by their means was the conception now, for the first time, connected with the uterus.
The brain presented itself as a large and soft coagulum, full of ample vessels. The ventricles of the heart were of equal capacity, and their walls of the same thickness. In the thorax, and covered by the ribs, three cavities, nearly of the same dimensions, were perceived; of these the lowest was occupied by the lungs, which are full of blood, and of the same colour as the liver and kidneys; the middle cavity was filled by the heart and pericardium; the superior cavity, again, was possessed by the gland called the thymus, which is now of very ample size.
In the stomach there was some chyle discovered, not very different in character from the fluid in which the embryo swam. It also contained some white curdled matter, not unlike the mucous sordes which the nurse washes particularly from between the folds of the skin of new-born infants. In the upper part of the intestines there was a small quantity of excrementitious or chylous matter; the lower bowels contained meconium. In the urinary bladder there was urine, and in the gall bladder bile. The intestinum cœcum, that appendix of the colon, was empty as in the adult, and apparently superfluous, not as in the lower animals—the hog, horse, hare, constituting as it were anotherstomach. The omentum, or apron, floated over the intestines at large like a thin and transparent veil or cloud.
The kidneys at this epoch are not yet formed into a smooth and continuous rounded mass, as in the adult, but are compacted of numerous smaller masses, as we see them in the calf and sturgeon, as if there were a renal globule or nipple placed at the extremity of each division of the ureter, from the orifice of which the urine distilled. Over the kidneys two bodies, first observed by Eustachius, are discovered, very abundantly supplied with blood, so that their veins, which anatomists designate as venæ adiposæ, are not much smaller than the emulgents themselves. The liver and spleen, according to their several proportions, are equally full of blood.
I may here observe, by the way, that in every strong and healthy human fœtus we everywhere discover milk; it is particularly abundant in the thymus gland, though it is also found in the pancreas, through the whole of the mesentery, and in certain lacteal veins and glands, as it seems, situated between the divisions of the mesenteric vessels. Moreover, it can be pressed and indeed sometimes flows spontaneously from the breasts of newly-bom infants, and nurses imagine that this is beneficial to the infant.
And it clearly appears that this fluid, which abounds in the ovum, is no excrementitious matter thrown off by the embryo, nothing like urine or sweat, because its relative quantity is diminished as the period of parturition approaches, when the fœtus is of course larger, and, as it consumes a greater quantity of nutriment, accumulates excrementitious matter more abundantly than it did in the first months of pregnancy. Let it be added, that the bladder is at this time distended with urine. For my own part I have never been able to discover that conduit for the urine, from the bladder to the umbilicus, which anatomists describe under the name of urachus; I have, on the contrary, frequently seen urine escaping by the penis, but never by any urachus, when the bladder was pressed upon with the hand.
So much for what I have observed with reference to the order of the parts in the development of the human fœtus.
In the fourth and last process the parts of the lowest state and order are produced, those, namely, that do not exist asneedful to the being or to the maintenance of the individual, but only as defences against external injury, as ornaments, or as weapons of offence.
The outermost part of all, the skin, with its several appendages,—cuticle, hair, wool, feathers, scales, shells, claws, hooves, and other items of the same description, may be regarded as the principal means of defence or protection. And it is well devised by nature, who, indeed, never does aught amiss, that these parts are the last to be engendered, inasmuch as they could never be of use or avail as defences until the animal was born. The common domestic pullet is therefore born covered with down only, not with feathers, like certain other birds which have to be speedily prepared for flight, because it has to seek its food on foot, not on the wing, and by active running about hither and thither. In like manner the young of ducks and geese, which feed swimming, have their feathers and wings perfected at a later period than their feet and legs. It is otherwise with swallows, however, which have to fly sooner than to walk, because they feed on the wing.
The down of the pullet begins to appear after the fourteenth day, the fœtus being already perfect in all its parts. When the feathers first show themselves, they are in the guise of points within the skin, but by and by the feathers project, like plants from the ground, increase in length, become unfolded, invest the whole body, and protect it against the inclemencies of the atmosphere.
Feathers differ from quills in form, use, place of growth, and order of production. The pullet is feathered before it has any quills, for the quill-feathers only grow in the wings and tail, and also spring more deeply, from the very lowest part of the integument, or even from the periosteum, and serve essentially as instruments of motion; the feathers again arise superficially from the skin, and are everywhere present as means of protection.
“Nails, hair, horn, and the like,” says Aristotle,[298]“are engendered from the skin; whence it happens that they change colour with the skin; for the white and black and particoloured are so in consequence of the colour of the skin whence theyarise.” In the bird, however, this is not so; for whatever the colour of the feathers, the skin is still never otherwise than of one tint, viz., white. And then the same feather or quill is frequently seen of different and often brilliant colours in different parts for the ornament of the creature.
In the human fœtus the skin and all the parts connected with it are in like manner perfected the last of all. In the earlier periods, consequently, we find neither lips, cheeks, external ears, eyelids, nor nose; and the last part to grow together is the upper lip in the course of the middle line of the body.
Man comes into the world naked and unarmed, as if nature had destined him for a social creature, and ordained him to live under equitable laws and in peace; as if she had desired that he should be guided by reason rather than be driven by force; therefore did she endow him with understanding, and furnish him with hands, that he might himself contrive what was necessary to his clothing and protection. To those animals to which nature has given vast strength, she has also presented weapons in harmony with their powers; to those that are not thus vigorous, she has given ingenuity, cunning, and singular dexterity in avoiding injury.
Ornaments of all kinds, such as tufts, crests, combs, wattles, brilliant plumage, and the like, of which some vain creatures seem not a little proud, to say nothing of such offensive weapons as teeth, horns, spurs, and other implements employed in combat, are more frequently and remarkably conferred upon the male than the female. And it is not uninteresting to remark, that many of these ornaments or weapons are most conspicuous in the male at that epoch when the females come into season, and burn with desire of engendering. And whilst in the young they are still absent, in the aged they also fail as being no longer wanted.
Our common cock, whose pugnacious qualities are well known, so soon as he comes to his strength and is possessed of the faculty of engendering, is distinguished by his spurs, and ornamented with his comb and beautiful feathers, by which he charms his mates to the rites of Venus, and is furnished for the combat with other males, the subject of dispute being no empty or vainglorious matter, but the perpetuation of the stock inthis line or in that; as if nature had intended that he who could best defend himself and his, should be preferred to others for the continuance of the kind. And indeed all animals which are better furnished with weapons of offence, and more warlike than others, fall out and fight, either in defence of their young, of their nests or dens, or of their prey; but more than all for the possession of their females. Once vanquished, they yield up possession of these, lay aside their strut and haughty demeanour, and, crest-fallen and submissive, they seem to consume with grief; the victor, on the contrary, who has gained possession of the females by his prowess, exults and boastfully proclaims the glory of his conquest.
Nor is this ornamenting anything adventitious and for a season only; it is a lasting and special gift of nature, who has not been studious to deck out animals, and especially birds only, but has also thrown an infinite variety of beautiful dyes over the lowly and insensate herbs and flowers.
Of certain paradoxes and problems to be considered in connexion with this subject.
Thus far have we spoken of the order of generation, whereby the differences between those creatures that are engendered by metamorphosis and those that are developed by epigenesis, as well as between those that are said to proceed from a worm and those that arise from an egg, have been made to appear. The latter are partly incorporated from a prepared matter, and are nourished and increased from a certain remaining matter; the former are incorporated from the whole of the matter present; the latter grow and are formed simultaneously, and after their birth continue to wax in size and finally attain maturity; the former increase at once, and from a grub or caterpillar grow into an aurelia, and are then produced, consummately formed, as butterflies, moths, and the like. Wherefore Aristotle, as Fabricius[299]observes: “As he assigns a sortof twofold nature to the egg, and a twofold egg in this kind, so does he assert a twofold action and a twofold animal engendered. For,” he proceeds, “from the first eggs, which are the primordia of generation, a worm is constantly produced; viz.: from the eggs of flies, ants, bees, silkworms, &c., in which some fluid is contained, and from the whole of which fluid the worm is engendered; but from the second eggs, formed by the worms themselves, butterflies are engendered and disclosed, viz.: flying animals contained in a shell, or follicle, or egg, which shell giving way the winged creature escapes; precisely as Aristotle[300]has it where he speaks of the egg of the locust.” Finally, whilst the higher animals produced from eggs are perfected by a succession of parts, the lower creatures that arise in this way, or that are formed by metamorphosis, are produced at one effort, as it were, and entire. And in the same way are engendered both those creatures that are said to arise spontaneously, by chance or accident, and derive their first matter or take their origin from putrefaction, filth, excrement, dew, or the parts of plants and animals, as well as those that arise congenerately from the semen of animals. Because this is common to all living creatures, viz.: that they derive their origin either from semen or eggs, whether this semen have proceeded from others of the same kind, or have come by chance or something else. For what sometimes happens in art occasionally occurs in nature also; those things, namely, take place by chance or accident which otherwise are brought about by art. Of this Aristotle[301]quotes health as an illustration. And the thing is not different as respects the generation, in so far as it is from seed, of certain animals: their semina are either present by accident, or they proceed from an univocal agent of the same kind. For even in fortuitous semina there is an inherent motive principle of generation, which procreates from itself and of itself; and this is the same as that which is found in the semina of congenerative animals,—a power, to wit, of forming a living creature. But of this matter we shall have more to say shortly.
From what has just been said, however, several paradoxes present themselves for consideration. For when we see the cicatricula enlarging in the egg, the colliquament concoctedand prepared, and a variety of other particulars all tending, not without foresight, to the development of the embryo, before the first rudiment or the merest particle of this is conspicuous, what should hinder us from believing that the calidum innatum and the vegetative soul of the chick are in existence before the chick itself? For what is competent to produce the effects and acts of life, except their efficient cause and principle, heat, namely, and the faculty of the vegetative soul? Therefore it would seem that the soul was not the act of the organic body possessing life in potentia; for we regard the chick with its appropriate form as the consequence of such an act. But where can we suppose the form and vital principle of the chick to inhere save in the chick itself? unless indeed we admitted a separation of forms and conceded a certain metamorphosis.
Now this appears most obviously where the same animal lives, as Aristotle has it, by or under a succession of forms, for example, a caterpillar, a chrysalis, a butterfly. For it is of necessity the same efficient, nutrient, and conservative principle that possesses each of these, although under different forms; unless we allow that there is one vital principle in the youth, another in the man, a third in the aged individual, or maintain that the forms of the grub and caterpillar are the same as those of the silkworm and butterfly. Aristotle has entered very fully into this subject, and we shall ourselves have more to say on it immediately.
It appears further paradoxical to maintain that the blood is produced, and moves to and fro, and is imbued with vital spirits, before any sanguiferous or locomotive organs are in existence. Neither is it less new and unheard-of to assert, that sensation and motion belong to the fœtus before the brain is formed; for the fœtus moves, contracting and unfolding itself, when there is nothing more than a little limpid water in the place of the brain.
Moreover, the body is nourished and increases before the organs appropriated to digestion, viz. the stomach and abdominal viscera, are formed. Sanguification, too, which is entitled the second digestion, is perfect before the first, or chylification, which takes place in the stomach, is begun. The excrementitious products of the first and second digestions, namely, excrement in the intestines, urine and bile in the urinary andgall bladder, are contemporaneous with the existence of the concocting organs themselves. Lastly, not only is there a soul or vital principle present in the vegetative part, but even before this there is inherent mind, foresight, and understanding, which from the very commencement to the being and perfect formation of the chick, dispose and order and take up all things requisite, moulding them in the new being, with consummate art, into the form and likeness of its parents.
In reference to this subject of family likeness, we may be permitted to inquire as to the reason why the offspring should at one time bear a stronger resemblance to the father, at another to the mother, and, at a third, to progenitors, both maternal and paternal, further removed? particularly in cases where at one bout, and at the same moment, several ova are fecundated. And this too is a remarkable fact, that virtues and vices, marks and moles, and even particular dispositions to disease are transmitted by parents to their offspring; and that while some inherit in this way, all do not. Among our poultry some are courageous, and pugnaciously inclined, and will sooner die than yield and flee from an adversary; their descendants, once or twice removed, however, unless they have come of equally well-bred parents, gradually lose this quality; according to the adage, “the brave are begotten by the brave.” In various other species of animals, and particularly in the human family, a certain nobility of race is observed; numerous qualities, in fact, both of mind and body, are derived by hereditary descent.
I have frequently wondered how it should happen that the offspring, mixed in so many particulars of its structure or constitution, with the stamp of both parents so obviously upon it, in so many parts, should still escape all mixture in the organs of generation; that it should so uniformly prove either male or female, so very rarely an hermaphrodite.
Lastly, many things are present before they appear, and some are begun among the very first which are completed among the very last, such as the eyes, the organs of generation, and the beak.
Several doubts and difficulties have thence arisen as to the principality and relative dignity of the several members, in which they who are fond of such things have displayed theiringenuity. Among the number: whether the heart gives life and virtue to the blood; or, rather, the blood to the heart. Whether the blood be extant for the sake of the body as matter, nourishment, and instrument; or, on the contrary, the body and its parts are the cause of the blood, and constituted for the sake of the vital principle which especially inheres in it. In like manner, whether the auricles or the ventricles of the heart are the chief, the auricles being the first to live and pulsate, the last to die. Further, whether the left ventricle, which in man is of greater length, and is also surrounded with thicker and more fleshy walls, and is regarded as the source of the spirits, be hotter, more spirituous, excitable, and excellent, than the right, which contains a larger quantity of blood, and is the last to become unstrung by death; in which the blood of the dying accumulates, congeals, and is deprived of life and spirit; to which, moreover, as to a fountain head, the first umbilical veins bring their blood, and from which they themselves derive their origin.
So much appears from careful observation of the order observed in the production of the parts, and certain other points that follow as deductions from these, and do not a little militate against the commonly received physiological doctrines, viz.: since it is manifest that sensation and motion exist before the brain, all sensation and motion do not proceed from the brain; from our history it is clearly ascertained that sense and movement inhere in the very first drop of blood produced in the egg, before there is a vestige of the body. The first scaffolding or rudiment of the body, too, which we have said is merely mucilaginous, before any of the extremities are visible, and when the brain is nothing more than a limpid fluid, if lightly pricked, will move obscurely, will contract and twist itself like a worm or caterpillar, so that it is very evidently possessed of sensation.
There are yet other arguments deduced from sense and motion whence we should infer that the brain was not so much the first principle of the body, in the way the medical writers maintain, as the heart, agreeably to Aristotle’s view.
The motions and actions which physicians stylenatural, because they take place involuntarily, and we can neither prevent nor moderate, accelerate nor retard them by our will, and theytherefore do not depend on the brain, still do not occur entirely without causing sensation, but proclaim themselves subject to sense, inasmuch as they are aroused, called forth, and changed thereby. When the heart, for example, is affected with palpitation, tremor, lipothymia, syncope, and with great variety in the extent, rapidity, and order or rhythm of its pulsations, we do not hesitate to ascribe these to morbific causes implicating, deranging its sensation. For whatever by its divers movements strives against irritations and troubles must necessarily be endowed with sensation.
The stomach and bowels, disturbed by the presence of vitiated humours, are affected with ructus, flatus, vomiting, and diarrhœa; and as it lies not in our power either to provoke or to restrain their motions, neither are we aware of any sensation dependent on the brain which should arouse the parts in question to motions of the kind.
It is truly wonderful to observe the effect of taking a solution of antimony, which we neither distinguish by the taste, nor find any inconvenience from, whether in the swallowing or the rejection. Nevertheless there is a certain discriminating sense in the stomach which distinguishes what is hurtful from what is useful, and by which vomiting is induced.
Nay, the flesh itself readily distinguishes a poisoned wound from one that is not poisoned, and on receipt of the former contracts and condenses itself, whereby phlegmonous tumours are produced, as we find in connexion with the stings of bees, gnats, and spiders.
I have myself, for experiment’s sake, occasionally pricked my hand with a clean needle, and then having rubbed the same needle on the teeth of a spider, I have pricked my hand in another place. I could not by my simple sensation perceive any difference between the two punctures; nevertheless there was a capacity in the skin to distinguish the one from the other; for the part pricked with the envenomed needle immediately contracted into a tubercle, and by and by became red, and hot, and inflamed, as if it collected and girded itself up for a contest with the poison for its overthrow.
The sensations which accompany affections of the uterus, such as twisting, decubitus, prolapse, ascent, suffocation, &c., and other inconveniences and irritations, do not depend onthe brain or on common sensation; yet neither are these to be presumed as happening without all consciousness. For that which is wholly without sense is not seen to be irritated by any means, neither can it be stimulated to motion or action of any kind. Nor have we any other means of distinguishing between an animate and sentient thing and one that is dead and senseless than the motion excited by some other irritating cause or thing, which as it incessantly follows, so does it also argue sensation.
But we shall have an opportunity of speaking farther of this matter when we discuss the actions and uses of the brain. Respect for our predecessors and for antiquity at large inclines us to defend their conclusions to the extent that love of truth will allow. Nor do I think it becoming in us to neglect and make little of their labours and conclusions who bore the torch that has lighted us to the shrine of philosophy. I am, therefore, of opinion that we should conclude in this way: we have consciousness in ourselves of five principal senses, by which we judge of external objects; but we do not feel with the same sense by means of which we are conscious that we feel—seeing with our eyes, we still do not know by them that we see, but by another sense or sensitive organ, namely, the internal common sensation or common sensorium, by which we examine those things that reach us through each of the external sensoria, and distinguish that which is white from that which is sweet or hard. Now this sensorium commune to which the species or impressions of all the external instruments of sensation are referred, is obviously the brain, which along with its nerves and the external organs annexed, is held and esteemed to be the adequate instrument of sensation. And this brain is like a sensitive root to which a variety of fibres tend, one of which sees, another hears, a third touches, and a fourth and a fifth smell and taste.
But as there are some actions and motions the government or direction of which is not dependent on the brain, and which are therefore callednatural, so also is it to be concluded that there is a certain sense or form of touch which is not referred to the common sensorium, nor in any way communicated to the brain, so that we do not perceive by this sense that we feel; but, as happens to those who are deranged in mind, orwho are agitated to such a degree by violent passion that they feel no pain, and pay no regard to the impressions made on their senses, so must we believe it to be with this sense, which we therefore distinguish from the proper animal sense. Now such a sense do we observe in zoophytes or plant-animals, in sponges, the sensitive plant, &c.
Wherefore, as many animals are endowed with both sense and motion without having a common sensorium or brain, such as earthworms, caterpillars of various kinds, chrysalides, &c., so also do certain natural actions take place in the embryo and even in ourselves without the agency of the brain, and a certain sensation takes place without consciousness. And as medical writers teach that the natural differ from the animal actions, so by parity of reason does the natural sense of touch differ from the animal sense of touch,—it constitutes, in a word, another species of touch; and whilst the one is communicated to the common sensorium, the other is not so communicated.
Further, it is one thing for a muscle to be contracted and moved, and another for it by regulated contractions and relaxations to perform any movement, such as progression or prehension. The muscles or organs of motion, when affected with spasms or convulsions from an irritating cause, are assuredly moved no otherwise than the decapitated cock or hen, which is agitated with many convulsive movements of its legs and wings, but all confused and without a purpose, because the controlling power of the brain has been taken away:—common sensation has disappeared, under the controlling influence of which these motions were formerly coordinated to progression by walking or to flight.
We therefore conceive the fact to be that all the natural motions proceed from the power of the heart, and depend on it; the spontaneous motions, however, and those that complete any motion which physicians entitle an animal motion, cannot be performed without the controlling influence of the brain and common sensation. For inasmuch as by this common sensation we are conscious of our perceptions, so also are we conscious that we move, and this whether the motion be regular or otherwise.
We have an excellent example of both of these kinds of motion in respiration. For the lungs, like the heart, are continually carried upwards and downwards by a natural movement, and are excited by any irritation to coughing and more frequent action; but they cannot form and regulate the voice, nor can singing be executed, without the assistance, and in some sort the command, of the sensorium commune.
But these matters will be more fully handled when we come to speak of the actions and uses of the brain, and to consider the vital principle or soul. So much we have thought fit to say by the way, that we might show the respect in which we hold our illustrious teachers, and our anxiety to carry them along with us in our labours.