THE REPRODUCTIVE ORGAX8. 757 



The muscular tissue of the prostate not only forms the chief part of 

 the stroma of the gland, bnt also forms a continuous layer inside the 

 fibrous sheath, as well as a layer surrounding the urethra, which is con- 

 tinous with the sphincter vesiese. 



PHYSIOLOGY OF THE SEXUAL ORGANS. 



Of the Female. In the process of development in the ovary of 

 individual Graafian vesicles, it has been already observed, that as each 

 increases in size, it gradually approaches the surface of the ovary, and 

 when fully ripe or mature, forms a little projection on the exterior. 

 Coincident with the increase in size, caused by the augmentation of its 

 liquid contents, the external envelope of the distended vesicle becomes 

 very thin and eventually bursts. By these means, the ovum and fluid 

 contents of the vesicle are liberated, and escape on the exterior of the 

 ovary, whence they pass into the Fallopian tube or oviduct, the fimbri- 

 ated 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 special 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 dis- 

 charge 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 im- 

 pregnation by the male, or even of sexual union. And it is now 

 established that a like maturation and discharge of ova, independently 

 of coition, occurs in mammalia, the periods at which the matured ova 

 are separated from the ovaries and received into the Fallopian tubes 

 being indicated in the lower mammalia by the phenomena of heat or 

 rut: in the human female, although not always with exact coincidence, 

 by the phenomena of menstruation. If the union of the sexes take 

 place, the ovum may be fecundated, and if no union occur it perishes. 



That this maturation and discharge occur periodically, and only 

 during the phenomena of heat in the lower mammalia, is made probable 

 by the facts that, in all instances in which Graafian vesicles have been 

 found presenting the appearance of recent rupture, the animals were at 

 the time, or had recently been, in heat; that on the other hand, there is no 

 authentic and detailed account of Graafian vesicles being found ruptured 

 in the intervals of the period of heat; and that female animals do not 

 admit the males, and never become impregnated, except at those periods. 



