MALE GENITAL ORGANS 



331 



tiated at the apex of the genital papilla. The epidermis is adherent to it, 

 but later becomes separated by the formation and splitting of an epithe- 

 lial plate, thus producing the reflection of skin called the prepuce. The 

 urogenital sinus becomes secondarily prolonged through the glans so as 

 to form the terminal part and external orifice of the urethra. The entire 

 urethra is divided into three parts: (i) the prostatic portion (pars pros- 

 tatica), which includes the outlet of the bladder together with the upper 

 end of the urogenital sinus, and receives the ejaculatory and prostatic 

 ducts; (2) the membranous part (pars membranacea) , which is the short 

 dilatable portion traversing the "pelvic diaphragm"; and (3) the long 

 cavernous portion (pars cavernosa), which is surrounded by the cavern- 

 ous vascular tissue. 



The scrotum develops as a median pouch at the dorsal end of the uro- 

 genital raphe. It is continuous above with the pair of large genital folds 

 which tend to encircle the base of the genital papilla, being deficient only 

 below (Fig. 329, A). At the stage when the testis and Wolffian body are 





PIG. 329. A, DIAGRAM OF THE EMBRYONIC EXTERNAL GENITAL ORGANS IN THE MALE; B, C, D, DIAGRAMS 

 OF THE DESCENT OF THE TESTIS. (After Eberth.) 



a., Anus; ep., epididymis; g., glans penis; g. f., lesser genital folds; g. g. f., greater genital folds; p. c., peri- 

 toneal cavity; p. v., processus vaginalis; r., raphe; t., testis; p. 1., parietal layer of the tunica vagmalis; 

 u. s., urogenital sinus; v. 1., visceral layer of the tunica vaginalis. 



still within the abdomen, lying behind the peritoneum, the peritoneal 

 cavity sends a prolongation, the processus vaginalis, over the pubic bone 

 into each half of the scrotum (Fig. 329, B). A large retroperitoneal 

 column of connective tissue, the gubernaculum testis, extends from the 

 posterior end of each testis into the depth of the scrotum. For reasons 

 still obscure, such as unequal growth or the shortening of this cord, the 

 testes pass down in front of the pubic bones, into the scrotum (Fig. 329, 

 C). The Wolffian duct becomes bent over the ureter as shown in Fig. 328, 

 and this important relation is found in the adult. Except on its dorsal 

 border, the testis is closely invested by the peritoneum of the processus 

 vaginalis. Later the distal part of the processus becomes separated from 

 the abdominal cavity by the obliteration of its stalk. The part remain- 

 ing about the testis is the tunica vaginalis, having a parietal and a visceral 

 layer as shown in Fig. 329, D. The descent of the testes is completed 

 shortly before birth, except in the occasional cases of "undescended testis." 



