DISCHARGE OF THE OVUM. 567 



in the immature ova. The matter in which the granules are 

 contained is fluid in the immature ova of all animals ; in some 

 it remains so ; but in others, as the human ovum, it subse- 

 quently becomes a consistent gelatinous substance. 



From the earliest infancy, and through the whole fruitful 

 period of life, there appears to be a constant formation, devel- 

 opment, and maturation of Graafian vesicles, with their con- 

 tained ova. Until the period of puberty, however, the pro- 

 cess is comparatively inactive ; for previous to this period, the 

 ovaries are small and pale, the Graafian vesicles in them are 

 very minute, few in number, and probably never attain full 

 development, but soon shrivel and disappear, instead of burst- 

 ing, as matured follicles do ; the contained ova are also inca- 

 pable of being impregnated. But, coincident with the other 

 changes which occur in the body at the time of puberty, the 

 ovaries enlarge, and become very vascular, the formation of 

 Graafian vesicles is more abundant, the size and degree of 

 development attained by them are greater, and the ova are 

 capable of being fecundated. 



Discharge of the Ovum. 



In the process of development of individual vesicles, it has 

 been already observed, that as each increases in size, it gradu- 

 ally approaches the surface of the ovary, and when fully ripe 

 or mature, forms a little projection on the exterior. Coinci- 

 dent with the increase of size, caused by the augmentation of 

 its liquid contents, the external envelope of the distended 

 vesicle becomes very thin and eventually bursts. By this 

 means, the ovum and fluid contents of the Graafian vesicle 

 are liberated, and escape on the exterior of the ovary, whence 

 they pass into the Fallopian tube, the fimbriated processes of 

 the extremity of which are supposed coincidentally to grasp 

 the ovary, while the aperture of the tube is applied to the 

 part corresponding to the matured and bursting vesicle. 



In animals whose capability of being impregnated occurs at 

 regular periods, as in the human subject, and most Mammalia, 

 the Graafian vesicles and their contained ova appear to 

 arrive at maturity, and the latter to be discharged at such 

 periods only. But in other animals, e. g., the common fowl, 

 the formation, maturation, and discharge of ova appear to 

 take place almost constantly. 



It has long been known, that in the so-called oviparous 

 animals, the separation of ova from the ovary may take place 

 independently of impregnation by the male, or even of sexual 

 union. And it is now established that a like maturation and 



