THE DEVELOPMENT OF THE UROGENITAL SYSTEM. 



423 



mesonephros (Fig. 374). The genital gland lies on the medial side of the 

 mesonephros and is attached to the latter by a sort of mesentery which becomes 

 the mesovarium in the female or the mesorchium in the male. The cephalic 

 portions of the ducts (Mullerian and mesonephric) lie close together in a ridge 

 on the lateral surface of the mesonephros; as they pass caudally they extend 

 around to the ventral surface of the mesonephros and approach the medial line, 

 and finally, in the pelvic region, the two ridges meet and fuse, forming the so- 

 called genital cord (Fig. 371). The genital cord thus contains the mesonephric 

 and Mullerian ducts, the latter fusing to form a single tube (the anlage of the 

 uterus and vagina, p. 419). It also contains the umbilical arteries. 



Kidney J 



Intestine - 



Round ligament! 

 (Inguinal ligament)! 



Umbilical artery! 



Suprarenal gland 



Bladder 



Umbilical vein 



Fig. 377. — From a dissection of the pelvic region of a female human fcetus of 7.5 cm. 



Kallmann's Atlas. 



Such a condition is found in embryos of about eight weeks. From this 

 time on, the processes of development follow divergent lines in the two sexes, 

 the differences becoming more marked from month to month. Certain struc- 

 tures persist and other disappear, according to the sex. The mesenteries and 

 ligaments undergo metamorphoses and the genital glands migrate caudally. 



Descent of the Testicles.— As the mesonephros atrophies, its mesentery 

 and the mesentery of the testicle are combined to form a single band of tissue 

 which, of course, is continuous with the inguinal ligament. The latter now 

 becomes the so-called gubemaculum testis (Hunteri), a strong band or cord 

 composed of connective tissue and smooth muscle. Its cephalic end is attached 

 to the epididymis; its caudal end pierces the body wall in the inguinal region and 



