grains. Among these grains there is a portion or acervulus, in which the grains are agglomerated in greater number, and, in the midst of these, a yelk-ball is found.

Fig. 40 represents this yelk-ball, bounded by a white, transparent

Fig. 40.

zone, which is called its zona pellucida. It is a perfect sphere, filled with vitellary corpuscles, oil globules, and puncta that swim in a transparent liquor. The sphere or yelk-ball lies amidst the cumulus of granules before mentioned, as may be seen in the figure, taken from Rudolph Wagner's Prodromus.

It is outside of, or beyond the white zone or zona pellucida, that are to be seen the smaller granules of the cumulus or acervulus, so that the globular ovum

above represented is bounded by the transparent or white zone. These outside granules are some remains of the granular membrane that lines the inner concentric membrane of the Graafian follicle.

Perhaps the physiologists go too far in calling it a granular membrane. It consists of innumerable grains that settle themselves, touching each other, upon the inner wall of the vesicle, like sediment in a vial. I do not deny that they deposit themselves thus under the forces of a vital affinity, and it is even probable that they do so; but whenever the vesicle is punctured, this so-called membrane becomes decomposed, and floats out as loose grains along with the yelk ball; great multitudes of them adhering to it; many being entirely disconnected, while some of them stick together in laminæ, or clusters, or acervuli.

This granular membrane, or tunica granulosa, is thickest, in general, at that segment of the Graafian vesicle which is nearest the surface of the albuginea, and there it forms a small heap-an acervulus or eumulus, which has been by Baer called the cumulus proligerus or discus proligerus. It is in the apex of this cumulus or cone that the egg is found, and it is generally among the debris of this acervulus that the microscope reveals the yelk, with its bright pellucid zone.

Upon referring again to the above figure, the Student will see that in the yelk-ball, amidst its vitellary corpuscles, there is pictured a clear, transparent, oval vesicle, with a dark spot upon it. This is the germinal vesicle, sometimes called Purkinjean vesicle, and the dark spot is the germinal spot, or maculæ germinativæ of Rudolph Wagner, which M. Coste calls the tuche embryonaire.

Such, in general terms, is the human ovary, which, I repeat, consists of a closed sac, filled with ovarian stroma, in which are developed ova within ovisacs usually called Graafian follicles. These ova are true yelks, about one-fifteenth of a line in diameter. In each unfecundated yelk is a germinal vesicle one-sixtieth of a Paris line in diameter, and having upon its inner surface a germinal spot consisting of dark granules-the germinal spot being one-two-hundredth or one-threehundredth of a line in diameter.

I have many times observed the numerous granules, or dark puncta, that may be inspected by placing thin slices of ovary on the field of a microscope. There are immense numbers of these points, which are, by some, supposed to be nuclei, or cytoblasts-the inchoate elements of ovarian ova. Such is the opinion of Martin Barry, who gives, in his papers, published in the London Phil. Trans., drawings of these appearances in the ova of various animals. Gerber's anatomy also contains a plate representing this microscopic view.

If this notion be indeed founded in truth, then each ovary should be held to contain, not fifteen ova only, but the nuclei of hundreds of thousands of them.

Perhaps, however, the microscopic view is not correct, and these points are acini of the gland, if the ovary is a gland. Supposing them to be acini, and that an acinus may, by some physiological act, be cast off from its connection with the stroma that produced it, and carry away with it, like an inoculated bud or like a spore, or a pollen grain, the metabolic and the plastic forces-by which to develop the ovarian ovule-still we have, in either case, the idea of a reproductiveness in creatures beyond imagination for copiousness.

The ovaries are abundantly supplied with nerves derived (Longet, t. ii. 543) from three or four branches that come off from the renal plexus, and proceed, in company with the ovaric artery, to the place of distribution. They are called the ovaric plexus, and distribute their terminal fibrils within the ovary, and in part, also, upon the uterus, thus connecting the two organs in a common bond of sympathies.

Regner de Graaf, of Delft, in Holland, where he died at the age of thirty-two years, on the 17th of August, 1673, published his work De Mulierum Organis Generationi Inservientibus in 1672, and gave, as I have said, his name to the ovarian vesicles, or ovi-capsules. They were by him considered to be ova, and were long, and even until lately, by many, regarded as ova; for no one, until recently, had acquired any correct notions of the ovum of the mammifera.

At p. 181, he says: "In cuniculis autem, leporibus, canibus, porcis, ovibus, vaccis et reliquis animalibus à nobis dissectis, ea vesicularum

ad instar, ut in avibus ovorum germina solent, sese dissecantium oculis exhibent; quæ in Testiculorum superficie existentia, communem tunicam hinc inde sublevant, atque ita per eam aliquando transparent ac si brevi exitum minarentur." His 15th plate represents the follicles as "ova." They are not ova, but merely ovisacs.

It is a title to immortality in the Republic of Letters, to have discovered the ovum of the mammal, and there has been a great contention as to the priority in this claim. It appears to me that, although one person may have first seen the object, so many individuals have been concerned in establishing and explaining the natural history and physiology of the fact, by laborious researches and patient efforts of reason, that no single person should be deemed entitled to all the credit: and it is certain, that the world is too much indebted to divers persons on this account, not to be willing to divide the honors of the career among many claimants. I feel no inclination to enter in favor of any particular person the lists of this controversy, in which I have no other than a common interest of gratitude to all the ingenious philosophers who have in this illumined my therapeutical path with floods of radiant light, freeing me from the errors and gropings of my blind predecessors, and enabling me clearly to perceive, and plainly understand many mysteries of physiology and therapeutics that were utterly hid from their eyes.

But the Student of medicine ought to be somewhat acquainted with the literary history of the subject, lest he wander, and be wholly lost among authorities that have now ceased to have any claim to his obedience. Let him, therefore, understand that a meeting was held at Breslau, in Silesia, in the year 1825, in honor of the fiftieth year of the Doctorate of Professor Blumenbach. At that meeting was presented a volume under the following title: Joan. Fried. Blumenbachio,

etc.

Summorum in Medicina honorum semisæcularia gratulatur ordo medicorum Vratislaventium, interprete Joanne Ev. Purkinje. P. P. 0. Subjectæ sunt symbolæ ad ovi avium historiam ante incubationem: cum doubus lithographis. Vratislavia, Typis Universitatis. This volume was printed in September, 1825, but was not published, being designed only for private distribution. An edition of it was afterwards published for sale at Leipsic, in 1830, 4to., of which a copy is now before me. I look I look upon Professor Purkinje's book as the first in the series of the works of reform as to our knowledge of the ovaria. This is the work in which was first made known the existence of the germinal vesicle, commonly called the Purkinjean vesicle of the bird's egg.

Professor Purkinje had interested himself in the investigation of the cicatricula, or tread of the hen's egg. He was examining it in a

vessel of water in order to learn the nature of the cumulus that lies directly underneath the cicatricula, and of which Fig. 41 is a repre

sentation. It has been very beautifully produced on wood by Mr. Gihon, from the original lithograph.

While, with a pair of dissecting needles, tearing the yelk asunder under water, and removing the broken-down masses with a pipette, he came upon a "most beautiful vesicle," partly adhering to the margin of the pore in the apex of the cumulus, and partly detached from its bed therein. His own words are: "Hæc dum lente ope perlustro, vesicula formosissima parte margini pori adhærens, parte libera haud parum mirabundo mihi offertur." Fig. 42 exhibits this appearance.

Fig. 43.

The cavity in which this Purkinjean, or germinal vesicle (the first that was ever seen), is contained, is represented by Purkinje as in the an nexed cut, Fig. 43, also copied from his lithograph. It is a cross section of a portion of the yelk-ball and the cumulus, with its cavity, in the hollow of which was found the Purkinjean

vesicle. The transparent vesicle thus revealed is almost as delicate in its structure as a soap bubble. It can be found only in eggs that have not been fecundated, such as the pullet's egg, or yelks taken out of the ovary, in which, according to Von Baer, it exists, even in the very smallest yelks. Fecundation abolishes it.

The Student has now a clear understanding as to the germinal or Purkinjean vesicle, discovered and made known in September, 1825. This Purkinjean vesicle is the germinal vesicle that is found inside of the unfecundated yelk, whether of birds or women or other animals.

The next publication in the order of important discovery, was the De ovi Mammalium et Hominis Genesi. Epistolam ad Academiam Imperialem scientiarum Petropolitanam, dedit Carolus Ernestus A. Baer. Zoologia Prof. Publ. ord. Regiomontanus, cum Tabula Aenea. Lips. 1827, 4to.

Such is the title of Von Baer's letter to the Imperial Academy of Sciences at St. Petersburg, on the subject of the ovum of the mammiferous quadrupeds.

In Von Baer's experiments, he, like Purkinje, never could find the vesicle in eggs already laid, but always detected it in even the smallest yelks of the egg bag. He supposes it to be the nucleus around which the matter of the yelk becomes subsequently aggregated. This was the case also in the molluscs, in the lumbricus and in the leech. These researches led him to the discovery of the mammiferous ovulum, in the following manner.

Having observed a very minute ovulum in the Fallopian tube of the bitch, and reflecting that such small ova could not consist of Graafian vesicles, which are much larger, and that the liquor of the Graafian vesicle could not so soon acquire the firmness and solidity of the tubal specimen, he was led by curiosity, rather than by the hope of seeing with the naked eye, through the several coats of the Graafian vesicles any ovula in the ovaries, to open one of the follicles with his scalpel, and placing the fluid that came forth upon the platine of his microscope: "Obstupui," says he, "profecto, cum ovulum ex tubis jam cognitum, tam clare viderem, ut cocus vix negaret. Mirum sane et inexpectatum, rem tam pertinacitur quæsitam, ad nauseam usque in quocunque compendio physiologico uti inextricabilem tractatum, tam facillimo negotio ante oculos poni posse." P. 12. He informs us that this ovulum may, in some specimens of the ovary, be seen through. the coats of the ovi-capsule.

Everybody seems willing to concede to Von Baer the honor of this discovery, which was effected two years later than that of Purkinje, viz., in 1827. But, notwithstanding his good fortune as the discoverer, he is not the true expositor of its nature, for he mistook the ovulum or yelk for the Purkinjean vesicle, and he says: "Demonstrabo enim mammalium ova vesiculis Purkinji reliquorum animalium comparandas esse, quas in animalibus nonnullis, molluscis, acepalis v. c. et lumbricis ovorum evolutionem antecedere clare me vidisse puto;" that is to say, "he will show that the mammal ovum is to be compared with the Purkinjean vesicle in other animals, and that the evolution of it precedes that of the ova in certain molluscous creatures, as he supposes to be verified by his observations."

At p. 32, he argues the identity of the nature of the Graafian ova and the ova of birds and spiders, which have a great quantity of vitelline corpuscles and but little liquid, while the Graafian ova bear but few corpuscles and much albuminous fluid. "Besides, they resemble eggs in possessing a vesicle situated in a cumulus, and