660 DEVELOPMENT OF THE KIDNEYS, 



At last, the testicles descend fairly to the bottom of the scrotum, 

 the gubernaculum constantly shortening, and the vas deferens 

 elongating as it proceeds. The convoluted portion of the efferent 

 duct, viz., the epididymis, then remains closely attached to the body 

 of the testicle; while the vas deferens passes upward, in a reverse 

 direction, enters the abdomen through the inguinal canal, again 

 bends downward, and joins its fellow of the opposite side ; after 

 which they both open into the prostatic portion of the urethra by 

 distinct orifices, situated on each side the median line. At the 

 same time, two diverticula arise from the median portion of the 

 vasa deferentia, and, elongating in a backward direction, underneath 

 the base of the bladder, become developed into two compound 

 sacculated reservoirs the vesiculss seminales. 



The left testicle is a little later in its descent than the right, but 

 it afterward passes farther into the scrotum, and, in the adult condi- 

 tion, usually hangs a little lower than its fellow of the opposite side. 

 After the testicle has fairly passed into the scrotum, the serous 

 pouch, which preceded its descent, remains for a time in communi- 

 cation with the peritoneal cavity. In many of the lower animals, 

 as, for example, the rabbit, this condition is permanent ; and the 

 testicle, even in the adult animal, may be alternately drawn down- 



ward into the scrotum, or retracted into 

 Fig. 250. the abdomen, by the action of the guber- 



naculum and the cremaster muscle. But 

 in the human foetus, the two opposite 

 surfaces of the peritoneal pouch, covering 

 the testicle, approach each other at the 

 inguinal canal, forming at that point a 

 constriction or neck, which partly shuts 

 off the testicle from the cavity of the 

 abdomen. By a continuation of this pro- 

 cess, the serous surfaces come actually 

 Formation of TCNICA VA- in contact with each other, and, adhering 



OINALIS TKSTIS. 1. Testicle , , . ,,-,. ~^ n 



nearly at the bottom of the Hero- together at thlS Situation (Fig. 2oO, 4), 



turn. 2 Cavity of tnnica va^nnlis. f orm a k^ Q f C i ca t r i X , Or UmbilicUS, bv 



:* Cavity of peritoneum. 4. Obliter- i i 



peritoneal ac. the complete closure and consolidation of 



which the cavity of the tunica vaginalis 

 (vj) is finally shut off altogether from the general cavity of the 

 peritoneum (3). The tunica vaginalis testis is, therefore, originally 

 a part of the peritoneum, from which it is subsequently separated 

 by the process just described. 



