652 



Comparative Morphology of Chordates 



PUBIC 

 SYMPHYS " 

 CORPUS 

 CAVERNOSUM 

 PENIS. 



CORPUS- 



CAVERNOSUM/ ; 



URETHRAE. / 



URETHRA - 



GLANDSr- 



GLANS- 

 PREPUCE 



-BULBOURETHRAL 

 GLAND. 

 BULBUS. 



Fig. 192. The human male urinogenital system. (After Sobotta. Courtesy, Neal 

 and Rand: "Chordate Anatomy," Philadelphia, The Blakiston Company.) 



forming the so-called "spermatic cord" (Fig. 492), whose essential 

 constituents are the vas deferens, the spermatic artery and vein 

 and the small arteries and veins associated with the vas deferens, 

 lymphatics, and nerves. The spermatic cord, of course, does not 

 enter the cavity of the bursa but, like the testis, lies external to the 

 tunica vaginalis — i.e., between the tunica and the adjacent fascia and 

 muscle of the wall of the bursa. 



In many mammals (marsupials, and commonly among insectivores, 

 rodents, and bats), the canal connecting each scrotal bursa with the 

 abdominal coelom remains permanently open. At the end of a breeding 

 season, the testes may be withdrawn into the abdominal cavity. At the 

 advent of another breeding season, they "descend" into the scrotum. 

 This withdrawal of the testis is effected by contraction of a muscle, 

 the cremaster, which is a continuation of the abdominal transverse 

 muscle (the internal oblique muscle sometimes involved with it) 

 along the wall of the communicating canal and into the wall of the 

 bursa inguinalis. In other mammals, including man, the communicating 

 canals normally close completely either before birth (in man) or during 

 infancy, the tunica vaginalis becoming entirely detached from the 

 abdominal peritoneum, and the testes are thereafter permanently 

 lodged in the scrotum. Incomplete closure of a canal is a common 

 abnormality in man. A loop of intestine may sag into the open canal, 

 producing an inguinal hernia. Sometimes (in man) one or both testes 

 fail to descend into the scrotum before the canal closes — the condition 



