DISSECTION OF THE DOG 9 



associated, as its name indicates, with the urethra, and lodged in a groove on 

 the urethral surface of the penis. 



The two crura penis, forming the radix penis, are covered by the ischio- 

 cavernous muscles. In the middle line, between the crura, the corpus eaver- 

 nosum urethrae forms a double expansion, the bulbus urethrce, also covered 

 by a muscle, the M. bulbo-cavernosus. 



The glans penis of the dog is of considerable length. Thinnest about the 

 middle, it expands into a swelling at each end. The caudal expansion known 

 as the bulbus glandis is the larger, and is developed on the dorsal side of the 

 os penis. From it the dorsal veins of the penis take origin. 



The smaller expansion of the glans forms the free extremity of the penis and 

 is more cylindrical in form than the bulbus glandis. Its terminal part is 

 pointed and has the urethral orifice at its apex. Running along the urethral 

 surface of the glans is a feeble fold of prepuce known as the frcenulum prceputii. 



Vv. dobsales penis. — The two dorsal veins of the penis arise in the erectile 

 tissue of the bulbus glandis. Running along the dorsum of the penis to its 

 root, they bend round the border of the ischia and form the main roots of the 

 internal pudendal veins. 



Aa. doksales penis. — The dorsal arteries of the penis lie lateral to the veins 

 of the same name. Each forms the largest terminal branch of the internal 

 pudendal artery of its own side, and, leaving the pelvis by curving round the 

 border of the ischium, can be readily followed to the glans penis. 



Nn. dorsales penis. — The dorsal nerves of the penis, branches of the 

 internal pudendal, accompany the dorsal vessels, each nerve lying lateral 

 to the artery which it follows. 



Dissection. — Cut through the roots of the brachial plexus and clean up the 

 ventral and lateral aspects of the thorax and abdomen. In doing this, 

 first define the extent and attachments of the cutaneous muscle as far as 

 the present dissection permits. Preserve the branches of the intercostal 

 and lumbar vessels and nerves which appear about midway between the 

 mid-dorsal and mid-ventral lines of the trunk. Observe that the branch 

 from the third or fourth intercostal nerve is of good size and crosses the 

 border of the latissimus dorsi muscle to reach the lateral aspect of the 

 arm. It is connected with a ventral thoracic nerve from the brachial 

 plexus. 



In removing the remains of the prepuce of the male, or the mammae of the 

 female, take care not to destroy the external pudendal vessels and the 

 external spermatic nerve which may be found embedded in an accumu- 

 lation of fat in the inguinal region. The artery and vein can generally be 

 traced to an anastomosis with branches from the cranial epigastric 

 vessels. 



