424 



TEXT-BOOK OF EMBRYOLOGY. 



is attached to the corium of the skin (Fig. 375). It plays an important part in 

 the descent of the testicle. The descent is brought about through the principle 

 of unequal growth. As the body grows in length, the gubernaculum grows 

 much less rapidly and, since the caudal end of the latter is fixed, the natural 

 result is the drawing downward of the testicle. This takes place gradually, 

 and at the end of the third month the testicle lies in the false pelvis ; at the end 

 of the sixth month close to the body wall at the inguinal ring. 



During the third month a second factor in the descent of the testicle appears. 

 This is an evagination of the peritoneum at the point where the gubernaculum 

 pierces the body wall. The evagination at first is a shallow depression, known 



Kidney 

 Mullerian duct 



Genital gland 

 Mesonephros 



Ureter 



Inguinal ligament 



Mesonephric duct 



Mullerian duct 



Apex of bladder 

 U- Bladder 

 Z_ Opening of uretei 



Opening of mesonephric duct 

 Opening oi Mullerian ducts 

 Rectum 

 Urogenital sinus 



Cloaca 



Genital tubercle 

 ~~ Genital ridge 

 Opening of cloaca 



FIG. 478. Diagrammatic representation of the urogenital organs in the " indifferent " stage. Hertwig. 



as the processus vaginalis peritonei, but continues to burrow through the body 

 wall and causes an elevation in the skin which is destined to become one side of 

 the scrotum (see p. 430) . The opening of the peritoneal sac into the body cavity 

 is the inguinal ring. In its descent the testicle passes through the inguinal ring 

 and comes to lie in the elevation in the skin or scrotum (ninth month) . Whether 

 its passage into the scrotum is the result of a traction by the gubernaculum is 

 not certain. The inguinal ring then closes by apposition of its walls and the 

 testicle lies in a closed sac which has been pinched off, so to speak, from the body 

 cavity (Fig. 376). 



