646 HANDBOOK OF PHYSIOLOGY. 



and numerous large ganglion cells surround the cortex. Pacinian bodies 

 are sometimes found in the substance of the organ. 



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

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

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

 tinuous with the sphincter vesicse. 



PHYSIOLOGY OF THE SEXUAL OKGANS. 



A. 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. Co- 

 incident 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 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 cor- 

 responding 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 ap- 

 pear 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 estab- 

 lished thai 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 dur- 

 ing 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 



