EXERCISE THE THIRD.
Of the upper part of the hen’s uterus, or the ovary.
The uterus of the fowl is divided by Fabricius into the superior and inferior portions, and the superior portion he calls the ovary.
The ovary is situated immediately beneath the liver, close to the spine, over the descending aorta. In this situation, in the larger animals with red blood, the cœliac artery enters the mesentery, at the origin, namely, of the emulgent veins, or a little lower; in the situation moreover in which in the other red-blooded and viviparous animals the vasa præparantia, tending to the testes, take their origin: in the same place at which the testes of the cock-bird are situated, there is the ovary of the hen discovered. For some animals carry their testicles externally; others have them within the body, in the loins, in the space midway from the origins of the vasa præparantia. But the cock has his testicles at the very origin of these vessels, as if his spermatic fluid needed no preparation.
Aristotle[131] says that the ovum begins at the diaphragm; “I, however,” says Fabricius, “in my treatise on Respiration, have denied that the feathered kinds have any diaphragm. The difficulty is resolved by admitting that birds are not entirely destitute of a kind of diaphragm, inasmuch as they have a delicate membrane in the place of this septum, which Aristotle calls a cincture and septum. Still they have no diaphragm that is muscular, and that might aid respiration, like other animals. But, indeed, Aristotle did not know the muscles.”
Thus is the prince of philosophers accused and excused in the same breath, his challenger being himself not free from error; because it is certain that Aristotle both knew the muscles, as I have elsewhere shown, and the membranes, which in birds are not only situated transversely in the direction of the cincture of the body, but extended in the line of the longitudinal direction of the belly, supplying the place of the diaphragm [of quadrupeds] and being subservient to respiration, as I have shown in the clearest manner in my disquisitions on the Respiration of Animals. And, passing over other particulars at this time, I shall only direct attention to the fact, that birds breathe with great freedom, and in singing also modulate their voice in the most admirable manner, their lungs all the while being so closely connected with their sides and ribs, that they can neither be dilated and rise, nor suffer contraction in any considerable degree.
The bronchia or ends of the trachea in birds, moreover, are perforate, and open into the abdomen (and this is an observation which I do not remember to have met with elsewhere), so that the air inspired is received into and stored up within the cells or cavities formed by the membranes mentioned above. In the same manner as fishes and serpents draw air into ample bladders situated in the abdomen, and there store it up, by which they are thought to swim more lightly; and as frogs and toads, when in the height of summer they respire more vigorously assume more than the usual quantity of air into their vesicular lungs, (whence they acquire so large a size,) which they afterwards freely expire, croaking all the while; so in the feathered tribes are the lungs rather the route and passage for respiration than its adequate instrument.
Now, had Fabricius seen this, he would never have denied that these membranes (with the assistance of the abdominal muscles at all events,) could subserve respiration and perform the office of the diaphragm, which, indeed, of itself, and without the assistance of the abdominal muscles, were incompetent to act as an instrument of respiration. And, then, the diaphragm has another duty to perform in those creatures in whom it is muscular or fleshy, viz., to depress the stomach filled with food, and the intestines distended with flatus, so that the heart and lungs shall not be invaded, and life itself oppressed in its citadel. But as there was no danger of anything of this kind in birds, they have a membranous septum, perfectly well adapted to the purposes of respiration, so that they have very properly been said to have a diaphragm. And were birds even entirely without anything in the shape of a diaphragm, still would Aristotle not be liable to criticism for speaking of the ova commencing at the septum transversum, because by this title he merely indicates the place where the diaphragm is usually met with in other animals. In the same way we ourselves say that the ovary is situated at the origin of the spermatic vasa præparantia, although the hen has, in fact, no such vessels.
The perforations of the lungs discovered by me (and to which I merely direct attention in this place,) are neither obscure nor doubtful, but, in birds especially, sufficiently conspicuous, so that in the ostrich I found many conduits which readily admitted the points of my fingers. In the turkey, fowl, and, indeed, almost all birds, you will find that a probe passed downwards by the trachea makes its way out of the lungs, and is discovered lying naked and exposed in one or another of the abdominal cells. Air blown into the lungs of these creatures with a pair of bellows passes on with a certain force even into the most inferior of these cells.
We may even be permitted to ask, whether in man, whilst he lives, there is not a passage from openings of the same kind into the cavity of the thorax? For how else should the pus poured out in empyema and the blood extravasated in pleurisy make its escape? In penetrating wounds of the chest, the lungs themselves being uninjured, air often escapes by the wound; or liquids thrown into the cavity of the thorax, are discharged with the expectoration. But our views of this subject will be found fully expressed elsewhere, viz., in our disquisitions on the Causes, Uses, and Organs of Respiration.
I return to the ovary and the upper portion of the fowl’s uterus, in which the rudiments of the eggs are produced. These, according to Aristotle,[132] in the first instance are small, and of a white colour; growing larger, they subsequently become of a paler and then of a deeper yellow.
The superior uterus of Fabricius, however, has no existence until after the hen has conceived, and contains the rudiments of ova within it; when it may be designated as a cluster of papulæ. And he therefore observes very properly, “The superior uterus is nothing more than an almost infinite congeries of yelks, which appear collected as it were into a single cluster, of a rounded form, and of every size, from that of a grain of mustard to that almost of a walnut or medlar. This multitude of vitelli is aggregated and conjoined very much in the manner of a bunch of grapes, for which reason I shall constantly speak of it as the vitellarium or raceme of yelks; a comparison which Aristotle himself made in speaking of the soft or scaleless fishes, when he says,[133] their ovary or roe is extruded agglutinated into a kind of raceme or bunch of grapes. And in the same way as in a bunch of grapes the several berries are seen to be of different sizes, some large, some small, some of very diminutive proportions, each hanging by its several peduncle, so do we find precisely the same thing in the vitellarium of the fowl.”
In fishes, frogs, crustacea, and testacea, however, matters are otherwise arranged. The ovary or vitellary here contains ova of one uniform size only, which being extruded increase, attain maturity, and give birth to fœtuses simultaneously. But in the ovary of the common fowl, and almost all the rest of the oviparous tribes, the yelks are found in various stages of their growth, from dimensions that are scarcely visible up to the full size. Nevertheless the eggs of the fowl and other birds, (not otherwise than in those cases where the eggs are all engendered and laid at the same moment,) ripen their fœtuses under the influence of incubation in the same nest, and produce them perfect, nearly at the same time. In the family of the pigeons, however, (which lay and incubate no more than two eggs in the same nest,) I have observed that all the ova crowded together in the ovary, with the exception of a single pair, were of the same dimensions; this pair was very much larger than any of the others, and already prepared to descend into the second or lower uterus. In these creatures, therefore, the number of young is great, not because of the multitude produced at a time, but of the frequency with which births take place, viz., every month. In the same way, among cartilaginous fishes, such as the skates, dog-fishes, &c., two eggs only come to maturity together, one of which descends from the right the other from the left corner of the uterus into the inferior portion, where they are cherished, and where they finally produce living fœtuses, precisely as happens among viviparous animals; in the ovary, nevertheless, there is almost infinite store of ova of various sizes—in the ray I have counted upwards of a hundred.
The ova of the other oviparous tribes are either perfected externally, as in the case of fishes, or they are concocted or matured, as in the instance of testacea, crustacea, and spiders. Testaceous animals lay their eggs amidst froth; the crustaceous tribes, such as the shrimp, crab, and lobster, bear them about with them, attached to certain appendages; and the spiders carry them about and cherish them, laid up in a kind of purse or basket, made of their web. The beetle rolls its eggs in dung, using its hind legs in the operation, and buries them. Now, in all these creatures the quantity of eggs is almost incredibly great: in fishes they form two oblong bladders or follicles, as may be seen in the carp, herring, and smelt, in all of which, as there is no uterus, but merely an ovary present, so is this sometimes crowded with ova to such a degree, that it comes to surpass the body in bulk.
Of such ovaries of the mullet and carp, salted and pressed, and dried in the smoke, was prepared that article of food in such request among the Greeks and old Italians, (called botorcha by the latter, ώά τάριχα, i. e. salted eggs, by the former,) and very similar, we may presume, to the masses which we find in the insides of our smoked herrings, and to the compact granular red-coloured roe of our lobsters. The article prepared from the salted roe of the sturgeon, which is called caviare, and resembles black soap, is still the delight of epicures.
In those fishes that are highly prolific such a quantity of eggs is engendered, that the whole abdomen can scarcely contain them, even when they are first produced, still less when they have grown to any size. In fishes, therefore, there is no part save the ovary dedicated to purposes of reproduction. The ova of these animals continue to grow without the body, and do not require the protection of an uterus for their evolution. And the ovary here appears to bear an analogy to the testicles or vesiculæ seminales, not only because it is found in the same place as the testes in the male, (the testes in the cock being situated, as we have said, close to the origin of the cœliac artery, near the waist, in the very same place as the ovary in the hen,) but because among fishes, in both sexes, as the time of spawning approaches, two follicles, alike in situation, size, and shape, are discovered, extending the whole length of the abdomen; which increase and become distended at the same period: in the male with a homogeneous milky spermatic matter, (whence the term milk or milt of fishes;) in the female with innumerable granules, which, from their diminutive size and close texture, in the beginning of the season, escape the powers of vision, and present themselves as constituting an uniform body, bearing the strongest resemblance to the milt of the male regularly coagulated. By and by they are seen in the guise of minute grains of sand, adhering together within their follicles.
In the smaller birds that lay but once a year, and a few eggs only, you will scarcely discover any ovary. Still, in the place where the testicles are situated in the male, there in the female, and not less obviously than the testicles of the male, you will perceive three or four vesicles (the number being in proportion to that of the eggs of which they are the rudiments), by way of ovary.
In the cornua of the uterus of snakes (which resemble the vasa deferentia in male animals), the first rudiments of the ova present themselves as globules strung upon a thread, in the same way as women’s bracelets, or like a rosary composed of amber beads.
Those ova that are found in the ovary of the fowl consequently are not to be regarded as perfect eggs, but only as their rudiments; and they are so arranged on the cluster, they succeed each other in such an order and of such dimensions, that they are always ready for each day’s laying. But none of the eggs in the ovary are surrounded with albumen; there the yelk exists alone, and each, as it enlarges, extricates itself from the general congeries of smaller ones, in order that it may the more readily find space to grow. Fabricius, therefore, is right when he says,[134] “The yelks which are on the surface of the cluster are larger than those of the middle, which are surrounded as it were by the larger ones. The very smallest of all the ova are situated towards the centre.” That is to say, those that grow acquire larger dimensions and become detached from the rest, and as this proceeds, the several yelks, besides their tunica propria, are invested with another from the ovary, which embraces them externally, and connects them with the base whence they spring. This coat is, therefore, entitled the peduncle by Fabricius, and its office is that of a foot-stalk, viz. to supply nourishment to the ovum, in the same way as fruit is nourished through the stalk by which it is connected with the tree. For this peduncle is a hollow membranous bond of union, extending from the foundation of the cluster [the stroma of the ovary] to the yelk, coming into contact with which, it is dilated and expanded in the same way as the optic nerve in the eye, and covers the vitellus with an external tunic. This perchance was what Aristotle called the στόλον ὸμφαλοώδην, or umbilical appendix, and described as forming a kind of tube. This peduncle includes numerous vessels, which are distributed on all sides around the yelk.
So much is accurately related by Fabricius; but he errs when he says, “This tunic does not surround the entire vitellus, but only extends upon it a little beyond the middle, very much in the manner of an acorn within its cup; whence it comes that the outer portion of the yelk, which is not invested by the membrane in question, presents itself free from vessels, and to appearance naked.” The membrane, nevertheless, surrounds the yelk completely; but on the outer aspect it is not very easily distinguished from the tunica propria, both of them being of extreme delicacy. Posteriorly, however, and where the yelk is turned towards the basis of the cluster, the tunic in question does not adhere to the vitellus, neither does it send any vessels to this part, but merely embraces it in the manner of a sac.
Each vitellus receives a distinct tunic from the ovarian basis; whence this is not to be regarded as the common uterus, since nothing is discovered here except the cluster or heap of ova, of many different sizes, proceeding from the same foundation.
Now, this foundation or basis is a body sui generis, arising on the spine of the feathered kinds, connected by means of large arteries and veins, and of a loose, porous, and spongy texture, in order that multitudes of ova may be produced from it, and that it may supply tunics to all; which tunics, when the yelks have grown to their full size, are distended by them, and then the tunics surround the vitelli, in the manner of sacks with narrower necks and more capacious bellies, very much like the flasks that are formed by the breath of the glass-blower.
Fabricius then proceeds: “The yelks, as they proceed from small beginnings, from the size of millet or mustard seeds, and are at first not only extremely small, but colourless, as Aristotle says, so do they increase by degrees, and, according to Aristotle, become first of a paler and then of a deeper yellow, until they have attained to the dimensions familiar to all.” I, however, have observed ova vastly smaller than millet seeds, ova which, like papulæ or sudamina, or the finest grains of sand, (such as we have indicated as found in the roe of fishes,) almost escaped the powers of sight; their places, indeed, were only proclaimed by a kind of roughness of the membranes.