THE SEXUAL ORGANS. 249 



liquor folliculi — of the density of the serum of the blood, con- 

 taining, almost always, isolated granules, nuclei, and cells, 

 which are scarcely anything more than detached portions of 

 the membrana granulosa, and do not originate in the fluid. 



In the germinal eminence, close upon the fibrous membrane 

 of the follicle, and therefore in the most prominent part of it, 

 is placed the 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 con- 

 tiguous part of the epithelium, which encompass it, as a sort of 

 ring or disc (discus proligerus, germinal disc, v. Baer), en- 

 closing 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 \ — T ^ /// ', which, though in certain 

 respects peculiar, nevertheless possesses the nature and consti- 

 tution of a simple cell. The cell-membrane, or vitelline mem- 

 brane, membrana vitellina, has the unusual thickness of 000^ 

 O005'", and, in microscopical figures, sur- Fig< 2 65. 



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

 clear, transparent ring, whence it has received 

 the name of zona pellucida. It is structure- 

 less, very elastic, and firm, so as to support 

 a considerable degree of extension without 

 being torn; and in chemical characters 

 corresponds, in every particular, with the membranes propria, 

 § 16. The light-yellow yelk, which in recent ovula completely 

 fills the vitelline membrane, is composed of a 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, , 02 /// , with clear contents, and a homo- 

 geneous, round, parietal nucleolus, 0003"' in size, the germinal 

 vesicle, vesicula germinativa (the " vesicle of Purkinje"), and 

 the germinal spot, macula germinativa (or " spot of Wagner") 

 as they are here termed. 



The parovarium (Nebeneierstock), a rudiment of the Wolffian 



Fig. 265. Human ovulum, from a follicle of the average size, x 250 diam.: a, 

 vitelline membrane (zona pellucida) ; b, external boundary of the yelk, and also in- 

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



