302 HAND-BOOK OF PHYSIOLOGY. 



than the kidneys (see Fig. 464), but by the more rapid growth of the 

 latter this relation is soon reversed. 



LATER DEVELOPMENT. 



The first appearance of the generative gland has been already de- 

 scribed: for some time it is impossible to determine whether an ovary or 

 testis will be developed from it; gradually however the special characters 

 belonging to one of them appear, and in either case the organ soon be- 

 gins to assume a relatively lower position in the body; the ovaries being 

 ultimately placed in the pelvis; while toward the end of foetal existence 

 the testicles descend into the scrotum, the testicle entering the internal 

 inguinal ring in the seventh month of foetal life, and completing its 

 descent through the inguinal canal and external ring into the scrotum by 

 the end of the eighth month. A pouch of peritoneum, the processus 

 vaginalis, precedes it in its descent, and ultimately forms the tunica 

 vaginalis or serous covering of the organ; the communication between the 

 tunica vaginalis and the cavity of the peritoneum being closed only a 

 short time before birth. In its descent, the testicle or ovary of course 

 retains the blood-vessels, nerves, and lymphatics, which were supplied to 

 it while in the lumbar region, and which are compelled to follow it, so to 

 speak, as it assumes a lower position in the body. Hence the explanation 

 of the otherwise strange fact of the origin of these parts at so consider- 

 able a distance from the organ to which they are distributed. 



Descent of the Testicles into Scrotum. The means by which 

 the descent of the testicles into the scrotum is effected are not fully and 

 exactly known. It was formerly believed that a membranous and partly 

 muscular cord, called the gubemacultwi testis, which extends while the 

 testicle is yet high in the abdomen, from its lower part, through the ab- 

 dominal wall (in the situation of the inguinal canal) to the front of the 

 pubes and lower part of the scrotum, was the agent by the contraction of 

 which the descent was effected. It is now generally believed, however, 

 that such is not the case; and that the descent of the testicle and ovary 

 is rather the result of a general process of development in these and 

 neighboring parts, the tendency of which is to produce this change in the 

 relative position of these organs. In other words, the descent is not the 

 result of a mere mechanical action, by which the organ is dragged down 

 to a lower position, but rather one change out of many which attend the 

 gradual development and re- arrangement of these organs. It may be 

 repeated, however, that the details of the process by which the descent 

 of the testicle into the scrotum is effected are not accurately known. 



The homologue, in the female, of the gubernaculum testis, is a struc- 

 ture called the round ligament of the uterus, which extends through the 



