986 



GENERATIVE APPARATUS. 



granulosa, consisting of round or polygonal granular cells. At the bottom oi 

 the ovisac, this epithelium forms a small mass — the cumulus proligerus (or 

 germinal eminence), in the centre of which is the ovulum or e^g of the mammal. 

 The contents (liquor folUcuU) is a clear yellow fluid, which becomes red on 

 admixture with blood when the vesicle ruptures. 



The ovulum, or ovum, is a cell about y^^ of an inch in diameter, enclosed in 

 the discus proligerus, or cumulus proligerus. The ovum is invested by a thick 

 membrane — the zona pellucida {membrana vitellina), formed of cells traversed by 

 radiating canals — the porous canalicuU (ova-tubes) ; its granular contents are 

 named the vitellus, or yolk ; and its (vesicular nucleated) nucleus, designated the 

 germinal vesicle, or vesicle of Purkinje, and lying at a certain point on the zona 

 pellucida, has in its centre a white patch — the germinal spot, or spot of Wagner. 



Balbiani has discovered, alongside the germinal vesicle, another, which he has 

 named the embryogenic vesicle. 



Vessels and nerves. — The thick, flexuous, arterial divisions are given off by 



the utero-ovarian artery; they 

 ^'-- ^^^- ramify in the spaces formed by 



the tunica albuginea, before 

 reaching the proper tissue by 

 entering the hilus. The veins, 

 are of large calibre, and form a 

 very rich network around the 

 gland — the bulb of the ovary ; 

 they terminate in the vena cava, 

 near the renal veins. The lym* 

 phatics are very abundant in the 

 medullary substance, and anas- 

 tomose in a network around the 

 follicles before they pass to the 

 sublumbar glands. Tiie nerves 

 emanate from the small mesen- 

 teric plexus. 



Development. — The ovary 

 of Solipeds is of great size in the 

 foetus, being often nearly as large 

 as in the adult animal. Fig. 

 530 exhibits the proportion between its volume and that of the uterus in a six 

 months' foetus. It becomes atrophied in aged animals. 



Functions. — The productive organs of the germ, or ovum, the ovaries are 

 the testicles of the female. They form the ova, and then at certain periods set 

 them at liberty. As the ova are contained in the Graafian vesicles, it is necessary 

 to study : 1 . The development of these vesicles. 2. Their rupture, or dehisence. 

 3, The phenomena occurring in them after rupture. 



Development of the Graafian vesicles. — The use of the Graafian vesicles is to 

 remove the ova from the ovary — to prepare their dehiscence ; consequently, the 

 development of these vesicles is subordinate to the presence of ova. The latter 

 begin to form among the cells of the germ-epithelium covering the surface of 

 the ovary ; then they become deeply embedded in the organ by means of Pfliiger's 

 cords, thrown out by the germ-epithelium. 



When the ovum is thus buried in the stroma of the ovary, the epithelium 



OVARIES, OVIDUCTS, AND UTERUS OF A FOETUS 

 (EQUINE). 



