Convoluted arteries of the ovary,
crossing it in nearly parallel lines.
The ovaries are supplied with blood by the spermatic arteries, which are of course considerably shorter in the female; they pass between the two layers of the broad ligament to the ovarium, assuming there a beautifully convoluted arrangement, very similar to the convoluted arteries of the testis. These vessels traverse the ovary nearly in parallel lines, forming numerous minute twigs, which have an irregular knotty appearance from their tortuous condition, and appear to be chiefly distributed to the Graafian vesicles. The external covering of the ovaries is formed by peritoneum, which here receives the name of Inducium; it envelopes the parenchymatous tissue of the gland called stroma, which is a dense laminar cellular tissue of a reddish colour; its external portion which is in contact with and firmly adherent to the indusium, is condensed into a species of covering of a firm structure and whitish colour, and is called the tunica albuginea of the ovary. In the substance of the stroma are embedded a number of vesicles of various sizes, which, although previously described by Vesalius and Fallopius, have been called Graafian vesicles, after De Graaf. These do not commonly become visible until the seventh year, from which period they gradually enlarge until puberty, when the ovaries increase in size, become softer and more vascular, and one or two of these vesicles may be observed to be larger, more developed, and projecting considerably from the surface of the gland.
The proper capsule of the Graafian vesicle is composed of two layers. The outer is formed of dense cellular tissue, in which are ramified many blood vessels; the inner layer is thicker, softer, and more opaque than the preceding, to which it is closely united, and from which it receives vascular twigs.
Ovum. The contained part or nucleus of the vesicle of De Graaf consists of, first, a granulary membrane, enclosing, secondly, a coagulable granular fluid; thirdly, connected with the granulary membrane on one side is a circular mass or disc of granulary matter, in the centre of which is embedded, fourthly, the ovum.
This disc, called by Baer the proligerous disc, presents in its centre on the side towards the interior of the vesicle, a small rounded prominence, called the cumulus, and on the opposite side a small cup-like cavity hollowed out in the cumulus. The cavity is for the reception of the ovum.[1]
Diagram of a section of the Graafian Vesicle and its contents, showing the situation of the Ovum.
a The granulary membrane. b The proligerous disc. c Ovum. d The inner and outer walls of the Graafian vesicle. e Indusium of the ovary. From T. W. Jones.
From the very minute size of the human ovum, and the difficulty of detecting it, the existence of this little corpuscule was not satisfactorily ascertained until modern times. Although De Graaf had observed ova in the Fallopian tube so early as 1668, which fact had been confirmed by the researches of Dr. Haighton and Mr. Cruickshank, still, as no traces of such ova had been discovered in the Graafian vesicle, and as it was evident that the Graafian vesicle, from its size, &c. could not pass along the Fallopian tube, it was concluded that the inner surface of the vesicle was a species of glandular structure which secreted the fluid with which it was filled, and which was analogous to the semen of the male testicle; hence, in former times, the ovaries were known by the name of testes muliebres. The celebrated anatomist Steno[2] first pointed out the analogy between these organs and the ovaries of the fish tribe: this view was afterwards supported by De Graaf,[3] and they have since continued to retain the name of ovaries.
To Professor von Baer, now of St. Petersburg, is due the merit of having first pointed out the distance of the ovum in the Graafian vesicle, and of thus putting beyond all doubt the accuracy of De Graaf’s observations, as well as those of Dr. Haighton and Mr. Cruickshank.