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surrounded with a proligerous layer. Therefore, a Graafian vesicle, in view of the ovary, and in general, of the maternal constitution, is the true ovum of the mammal. Vesicula ergo Graafiana cum ad ovarium generatimque ad corpus maternum respiciamus, ovum sane est mammalium.'" Von Baer, notwithstanding the tyranny of the schools, almost saw the real truth; for he remarks upon the fact, that the whole Graafian ovum cannot, as in birds, be transferred to the vector tube. "Hence in mammals," says he, "the inner vesicle (the true ovum) contains a richer vitellary matter, and as to the evolution of the fœtus, it certainly proves itself to be a true ovum." In saying this, he was nearly free from the shackles of his scholastic prejudice. They were strong enough, however, to cause him to write of the ovulum, "Ovum fetale dici possit in ovo materno. Mammalia ergo habent ovum in ovo; aut si hac dicendi formula uti licet, ovum in secunda potentia."

The Student, in reading the above, will candidly admit Von Baer's claims, though he will perceive how checked he was by the bonds of an old way of thinking. After all, the egg within an egg was, in his eyes, the true, separate, independent yelk-ball of the mammal.

The ovum of the bitch is th to 'th of a Paris line in diameter, according to Von Baer.

Now, notwithstanding M. Von Baer, as by the foregoing appears, is the discoverer of the mammal ovum, it is not doubted that Messrs. Prevost and Dumas had seen it in 1825-the year in which Purkinje detected the germinal vesicle. They, on two occasions, turned out and saw the ovulum of the Graafian ovi-capsule in the rabbit. Yet, the glory is Von Baer's.

As to the history of the Purkinjean vesicle in the mammal ovule, it appears now to be settled that the honor of its discovery belongs to Professor Coste, of the College of France, though several Germans have attributed it also to Von Baer.

M. Coste, in his Histoire Générale et Particulière du Développement des Corps Organisés, says:

"I was at first accused of having copied M. Baer; but, inasmuch as the opinions I had set forth were diametrically opposed to those of that great physiologist, the public early did justice to a reproach so unfounded, and the improper criticisms of Mr. Robert Froriep were promptly repelled by Bernhardt himself, in his inaugural thesis, Symbola ad Ovi Historiam, p. 25. This reproach having been set aside, an attempt was next made to bestow upon others the credit it was im possible to assign to M. Von Baer. It was pretended that the discovery was made at the same time, or nearly at the same time, by M. Coste

in France, M. Bernhardt in Germany, and Mr. T. Wharton Jones in England. As to M. Bernhardt, it is enough for me to refer to that author's preface, in which he declares that his experiments were instituted for the purpose of ascertaining the correctness of my observations. Mr. Jones's publication is later by one year than mine; a statement that might suffice for the present occasion, were it not that that physiologist has himself fully recognized my rights as to the priority of discovery, in his report on Ovology in the Brit. and For. Med. Review, No. 32, 1843, a paper in which he lays no claim to it himself, but attributes it to me."

Thus far M. Coste, whose remark as to Bernhardt's preface is correct, as well as his citation of Mr. Jones's paper.

Mr. T. Wharton Jones's words are as follows:

"By the discovery of the germinal vesicle, in the mammiferous ovarian ovum, the complete analogy between the latter and the ovarian ovum of the bird, &c., was established, and Baer's error regarding it dissipated. The correct view of the matter had been suspected by Purkinje, but he and Valentin had in vain searched for a germinal vesicle, and it was only on renewing their investigations, after the announcement that such a vesicle had been discovered in the rabbit's ovum by M. Coste, that they, Wagner, and others in Germany, were successful in finding it. M. Coste, therefore, as Bischoff observes, must, notwithstanding his very imperfect description and delineation of the germinal vesicle, be considered as its first discoverer."

This, it appears to me, is enough to enable the Student to see clearly the whole case; and I shall not further cite M. Coste, in his warm reclamations against M. Bischoff of Giessen.

It is much to be regretted that, amidst the tranquil pursuits of letters and philosophy, there should arise occasions for reproach—the more, as so much honor always remains to be shared by the diligent members of the Republic. The world is very ready to acknowledge the services and merits of all those wise, learned, and good men, who, like Purkinje, Baer, Coste, Wagner, Jones, Pouchet, and Bischoff, have in their publications endowed mankind with an impayable benefit.

The discovery of the mammal ovum was rendered complete by the detection, in 1830, of the macula germinativa or germinal spot, which is diversely attributed to Professor Rudolph Wagner and Mr. T. Wharton Jones; and it may be esteemed a conceded point that it was contemporaneously observed, as it was contemporaneously described, by those gentlemen in Germany and in England.

The germinal spot is, by Wagner, in his Prodromus Historic Generationis Hominis atque Animalium, page 4, called primitive Keimschicht

and maculæ germinative. Professor Wagner, in a note, page 44, Part I., Elements of Physiology, says:—

"I was myself the first to discover the germinal macula. I also described and figured the whole ovum in its successive stages with greater care and sequence than had yet been done."

Wharton Jones says: "At one side of the germinal vesicle there is a small, round, dark spot, discovered and described contemporaneously by Rudolph Wagner and the author of this report." (Brit. and For. Med. Review, 1843, p. 517.)

The germinal spot is from one-two-hundredth to one-three-hundredth of a Paris line in diameter. It consists of a collection of grains. Wagner's words, Prodromus, p. 4, are: "If the germinal vesicle in man and in the mammifers be carefully examined with the microscope at four hundred or five hundred diameters, there will be seen in one part of the vesicle a dark round spot.”

In this way, he found it in mammals, birds, scaly amphibia, cartilaginous fishes, arachnids, certain crustaceans, all mollusks, conchaceans, echinoderms, medusans, and polyps. Upon a more minute examination, under still higher powers, there is seen a compressed orbicular stratum of a lenticular shape, composed of minute molecules, closely agglutinated in form of an acervulus, &c. &c.

This granulous germinal stratum appears to Wagner to be the true living animal germ, existing antecedently to the act of impregnation. "Hoc stratum granulosum germinativum, germen animale verum et vivum jam ante prægnationem præformatum esse videtur."

Having now laid before the Student this account of the ovary, I shall annex a copy of M. Coste's magnified view of the ovarium from his grand atlas. In that superb plate, the figure is ten inches in its greatest diameter. Mr. Gihon has reduced it to this size. It was necessary to make it not more than four inches in diameter.

M. Coste's intention was not merely to exhibit the shape of the Ovary greatly magnified, but to show the internal structure of it, and the various phases of the ovarian ova and their ovi-capsules during their maturation and the dehiscence and evacuation of the follicles. It is the left ovarium that is represented. The expanded fimbria p, of the Fallopian tube p, is seen at the lower and right extremity of the drawing. Near this angle is seen a Graafian follicle v, the dehiscence or rupture of which has allowed a yelk, surrounded by its proligerous disk or cumulus, to escape. The opening has taken place through the tunica albuginea and the peritoneal coat, and the ovule marked œ is still resting upon the exterior surface. Just above it is seen another less mature vesicle v, and a still smaller one above that,

while farther to the left is a very small one. The line of incision passes, near its lower angle, across a pretty large and superficial folli

Fig. 44.

f

cle, one-half of which is seen through the coats of the ovary, while the other half is quite uncovered by the dissection, which has laid the organ open to view. To the right and upwards from this point is seen an emptied Graafian cell v, in which e is the outer surface of the whole cell. Atv is the point of dehiscence, through which the egg escaped. This Graafian cell consisted of two coats or membranes, one contained within the other. The broken lacinia of the double ovisac are seen at the upper end, near the margin of dehiscence, where they are marked g and i. These two coats are better represented in the follicle at the upper and left extremity of the cut-in which their floating and distinct membranes are seen at e and at i, whereas g indicates the granular deposits upon the inside of the follicle, which is called the tunica granulosa, or granular membrane. This granular membrane is so little tenacious that upon puncturing and compressing a cell, it flows out with the water, and appears upon the microscope as a collection of innumerable grains, that are probably cytoblasts.

Very near the superficial segment of this ovarian ovisac is seen the ovulum inclosed within its proligerous cumulus.

Fig. 45.

In order that the Student may here have a more complete idea of the ovary, I repeat the figure 45 of the human egg, taken from Rudolph Wagner's Prodromus Histor. Generationis, in which is seen the pellucid ring, surrounding and inclosing a quantity of yelk corpuscles, among which, near the top, rests a transparent vesicle with a dark spot upon it. The pellucid ring is the zona pellucida of the egg, outside of which is a quantity of granulous membrane that always comes out of the Graafian follicle sticking to the pellucid zone. It is necessary to remark that this figure is greatly magnified, for a very strong sight is required to enable any one to see without a lens the egglet, whose diameter is but the twentieth of a Paris line. The grains inside of the pellucid zone are grains of yelk-or vitellary corpuscles. They are yelk, true yelk, like that of a bird's egg. The oval transparent vesicle within them is the germinal vesicle, and the dark spot upon that vesicle is the macula germinativa-tache embryonaire-or germinal spot.

If the Student will look upon the germinal spot as the nucleolus, the germinal vesicle as the nucleus, and the vitellary membrane as the cell, he will have an idea of a true independent cell, possessing the metabolic and plastic forces that can enable it to develop itself wherever the proper cytoblastema, or pabulum, is afforded to it for that purpose-i. e. in the ovary, the tube, or the womb.

The production within the ovary of an ovum containing within it a germ, possessing, after its fecundation by the male, the power of evolution solely in the direction and dimensions of its own genus and species, is one of the most mysterious and wonderful works of God; one well fitted to overwhelm the mind with astonishment and make us feel amazed at the vastness and the indispensableness of those forces that are communicated by a Divine power to the simple and microscopic elements of the macula germinativa.

Burdach, in his Physiology, t. i. 87, speaking of the tubular ovary in which the materials of yelks are secreted in the cavity of the ovaries, in order to become ova, presumes this to be the mode in which ova are formed in all the insects, in most of the inferior crustaceans, in worms, and in certain mollusks. "Moreover," says he, "there is not the least doubt that the substances of which the egg is