642 SPECIAL HISTOLOGY. 



egg (ovulum), imbedded in the cells of which the eminence is composed, 

 and retained in its position by them. When the follicle bursts, or is 

 ruptured, the ovulum escapes, surrounded by the cells of the cumulus, 

 and the contiguous part of the epithelium, which encompass it, as a sort 

 of ring or disc (discus proligerus, germinal disc, v. Baer), enclosing it, 

 however, entirely, and by no means only attached to it in its greatest 

 breadth. The ovulum itself is a spherical vesicle, measuring when 

 mature 1-81-10 of a line, which, though in certain respects peculiar, 

 nevertheless possesses the nature and constitution of a simple cell. The 

 cell-membrane, or vitelline membrane, membrana vitellina, has the un- 

 usual thickness of 0*004 0*005 of a line, and, in microscopical figures, 



surrounds the contents, or yelk (vitellus), as a 

 Fig.2G5. . , * . , 



clear, transparent ring, whence it has received 



the name of zona pellucida. It is structureless, 

 very elastic, and firm, so as to support a consi- 

 derable degree of extension without being torn ; 

 and in chemical characters corresponds, in every 

 particular, with the membrance proprice, 16. 

 The light-yellow yelk, which in recent ovula com- 

 pletely fills the vitelline membrane, is composed of viscid fluid, having 

 numerous minute, pale granules dispersed in it, with which, in the 

 mature ova, some fatty granules are also associated, and, in the fully- 

 formed ovum, contains, excentrically, a well-marked vesicular nucleus, 

 0*02 of a line, with clear contents, and a homogeneous, round, parietal 

 nucleolus, 0-003 of a line in size, the germinal vesicle, vesicula germina- 

 tiva (the "vesicle of Purkinje"'), and the germinal spot, macula ger- 

 minativa (or " spot of Wagner") as they are here termed. 



The parovarium (Nebeneierstock)- a rudiment of the WollBan body of 

 the embryo, consists of a certain number of canals, 0-15-0-2 of a line 

 in diameter, diverging from the hilus ovarii into the " bat's wing," 

 which in Man neither open into the ovarium nor are connected with 

 any other parts, and contain nothing but a little clear fluid. The tubes 

 are formed of a fibrous membrane, 0*020-0-024 of a line thick, and of a 

 single layer of pale, cylindrical, probably ciliated cells, and are of in- 

 terest only as the remains of an embryonic structure. 



The arteries of the ovary, derived from the aa. spermatica and uterina, 

 and forming numerous minute trunks between the lamella of the broad 

 ligaments, enter from the inferior border of the ovary, run in a serpen- 

 tine course in the internal portion of the stroma, and terminate partly 

 in the stroma itself and in the t. albuginea, but chiefly in the walls of 

 the Graafian follicles, where they form an exterior more coarse, and an 



FIG. 265. Human ovulum, from a follicle of the average size, magnified 250 diam. : a, 

 vitelline membrane (zona pellucida) ; 6, external boundary of the yelk, and also internal 

 boundary of the yelk-membrane ; c, germinal vesicle, with the germinal spot. 



