870 DEVELOPMENT [CH. LTX. 



The manner in whicli the ovary is formed is described in outline 

 in Chapter LVIII. (p. 825); the testis is formed in a similar way, 

 only the downgrowths of cells which become nests of cells to form 

 ova and Graafian follicles in the female, become hollowed out as 

 seminiferous tubules in the male. 



For some time it is impossible to determine whether an ovary or 

 testis will be developed ; gradually, however, the special characters 

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

 begins to assume a relatively lower position in the body ; the ovaries 

 are thus ultimately placed in the pelvis, and the testicles descend 

 into the scrotum; the testicle enters the internal inguinal ring in 

 the seventh month of foetal life, and completes 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 t 

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

 or serous membrane of the organ ; the communication between the 

 tunica vaginalis and the cavity of the peritoneum is 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 accompany it as 

 it assumes a lower position in the body. Hence it is that these 

 parts originate at so considerable a distance from the organ to which 

 they are distributed. 



The gubernaculum testis is a cord, partly fibrous, partly muscular, 

 which extends while the testicle is yet high in the abdomen, from 

 its lower part, through the abdominal wall (in tho situation of 

 the inguinal canal) to the front of the pubes and lower part of the 

 scrotum. The homologue, in the female, of the gubernaculum testis 

 is the round ligament of the uterus, which extends through the 

 inguinal canal, from the outer and upper part of the uterus to the 

 subcutaneous tissue in front of the symphysis pubis. 



At a very early stage of foetal life, the Wolffian ducts, ureters, 

 and Miillerian ducts open into the lower extremity of the intestine, 

 which constitutes for the time a common receptacle or cloaca. This 

 opens to the exterior of the body through a part corresponding with 

 the future anus, an arrangement which is permanent in reptiles, 

 birds, and some of the lower mammalia. In the human foetus, how- 

 ever, the intestinal portion of the cloaca is cut off from that which 

 belongs to the urinary and generative organs ; a separate passage or 

 canal to the exterior of the body, belonging to these parts, is called 

 the sinus urogenitalis. Subsequently, this canal is divided, by a 

 process of division extending from before backwards or from above 

 downwards, into a "pars urinaria" and a "pars genitalis." The 

 former, continuous with the urachus, is converted into the urinary 

 bladder. 



