MALE GENITAL ORGANS OF THE DOG 595 



The cavernous spaces of the glans penis are venous in character. Von Frey has sho-wn that 

 the spaces of the pars longa are continuous with veins which come from the penile layer of the pre- 

 puce, and have no arterial blood supply. The erectile tissue of the bulbus glandis receives its 

 blood by veins which come from the pars longa. This arrangement is considered to account for 

 the erection of the bulbus during copulation, and the slowness with which erection subsides. 



The prepuce forms a complete sheath around the anterior part of the penis. 

 The outer layer is ordinary integument. The inner layers are thin, reddish in 

 color, and glandless. The penile layer is closely attached to the pars longa glandis, 

 more loosely to the bulbus glandis. There are many lymph nodules in these layers, 

 which are specially large and often prominent in the fundus of the preputial cavity. 

 The protractor muscles arise in the xiphoid region and decussate posteriorly around 

 the extremity of the prepuce. 



The pelvic part of the urethra is relatively long. Its first part is enclosed in 

 the prostate.'- At the ischial arch the urethra has a well-developed bulb, formed 

 by an enlargement here of the corpus cavernosum urethrse. It is divided by a 

 median furrow and septum (Septum bulbi urethris) into two lateral lobes or hemis- 

 pheres (Hemispheria bulbi urethrse), and is covered by the strong but short bulbo- 

 cavemosus muscle. The other erectile bodies have been described. The urethral 

 muscle is very strong; it encircles the urethra from the prostate backward and has 

 a median raphe dorsally. The ischio-urethral muscle arises from the tuber ischii 

 and ends on a fibrous ring at the symphysis ischii which encircles the dorsal veins 

 of the penis. 



'This is clinically important, since enlargement of the prostate may interfere with mic- 

 turition. 



