. The chordates. Chordata. 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. T
. The chordates. Chordata. 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—, 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 At the end of a breeding season, the testes may be withdrawn into the abdominal cavity.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. Please note that thes
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