THF. UROGENITAL SYSTEM. 261 



on its medial side, to the spermatic cord (Fi^. iii, d). It 

 leaves the spermatic cord at the internal inguinal ring and, 

 curving over the ureter (Fig. iii, d), bends craniad and 

 api)roaches the vas deferens of the opposite side dorsad of the 

 neck of the bladder (Fig. iii,/"). The two vasa deferentia 

 pass caudad together as far as the cranial border of the pubis. 

 There they enter the prostate gland {g), pierce the dorsal wall 

 of the neck of the bladder, and open close together on tlie inner 

 surface. The two openings are separated by a slight elevation, 

 the veru montanum. 



The Urethra (Fig. ill, //). — The urethra is the common 

 urinogenital duct which is formed by the union of the neck of 

 the bladder (/") and the vasa deferentia {e) dorsad of the cranial 

 border of the pubis. It extends thence to the end of the penis. 

 It is divided into three portions. 



1. The prostate portion is the commencement of the 

 urethra; it is surrounded by the prostate gland {g). 



2. The membranous portion (//) extends from the prostate 

 portion to a point between the crura of the penis. This por- 

 tion is surrounded by the thick compressor urethrse muscle, so 

 that its wall appears much thicker than it really is. 



3. The spongy portion (pars cavernosa) extends along the 

 ventral side of the penis to its end in the groove between the 

 corpora cavernosa penis. At its beginning is an enlargement 

 formed by the bulbocavernosus muscle. This is known as the 

 bulbus urethrae. The walls of the spongy portion are thick 

 and vascular and form the corpus cavernosum urethrae or 

 corpus spongiosum. At its end the corpus cavernosum urethrae 

 is greatly enlarged and forms the glans penis {in). 



Glands of the Urethra. — i. The prostate (Fig. i ii, ^) is a 

 bilobed gland lying on the dorsal wall of the urethra and sur- 

 rounding the ends of the vasa deferentia {c). It opens into the 

 urethra at its beginning by numerous small ducts visible to the 

 naked eye on the inner surface of the urethra. 



2. The bulbourethral or Cowper's glands (Fig. in, i). — 

 There are two bulbourethral or Cowper's glands, one on either 

 side of the bulbus of the urethra between the ischiocavernosus 

 and bulbocavernosus muscles. Each has a covering of muscle- 



