684 



REPRODUCTION. 



FIG. 233. 



comparatively straight, but increases in length, and is finally known as 

 the vas deferens. 



As the testicles descend still farther in the abdomen, they continue 

 to grow, while the Wolffian bodies become smaller ; and at last, when 

 the testicles have arrived at the internal inguinal ring, the Wolffian 

 bodies are no longer recognizable. In the human foatus, the testicles 

 reach the internal inguinal ring about the end of the sixth month 

 (Wilson). 



During the seventh month a protrusion of the peritoneum takes place 

 through the inguinal canal, in advance of the testicle ; and as this 

 organ passes into the scrotum, loops of muscular fibres are given off 

 from the lower border of the internal oblique muscle of the abdomen, 

 extending downward over the testicle and spermatic cord. They form 

 afterward the cremaster muscle. 



At last, the testicles descend quite to the bottom of the scrotum. 

 The convoluted portion of the efferent duct, namely, the epididymis r 

 remains attached to the testicle ; while the vas deferens passes up- 

 ward, 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, on either side 

 of the median line. At the same time, two 

 diverticula arise from the median portion of 

 the vasa deferentia, and, elongating in a back- 

 ward direction, beneath the base of the blad- 

 der, become developed into sacculated reser- 

 voirs, the vesiculae seminales. 



The left testicle is a little later in its de- 

 scent than the right ; but it passes farther 

 into the scrotum, and, in the adult condition, 

 usually hangs lower than that of the opposite 

 side. 



After the testicle has passed into the scro- 

 tum, the serous pouch, which preceded its 

 descent, remains for a time in communication 

 with the general cavity of the peritoneum. 

 In many quadrupeds, as, for example, the 

 rabbit, this condition is permanent ; and the 



testicle may be either drawn downward into the scrotum, or retracted 

 into the abdomen, by the alternate action of the gubernaculum and the 

 cremaster muscle. In the human fostus the opposite surfaces of the 

 peritoneal pouch approach each other at the inguinal canal, forming a 

 constriction, which partly shuts off the testicle from the cavity of the 

 abdomen. By a continuation of this process, the serous surfaces come 

 in contact, and, adhering together at this situation (Fig. 233, 4 ), form a 

 kind of cicatrix, by which the cavity of the tunica vaginalis ( 2 ) is shut 

 off from the general cavity of the peritoneum ( 3 ). The tunica vaginalis 



Formation of the TUNICA VAGI- 

 NALIS TESTIS. 1. Testicle near- 

 ly at the bottom of the scrotum. 



2. Cavity of tunica vaginalis. 



3. Cavity of peritoneum. 4. 

 Obliterated neck of peritoneal 



