178 THE REPRODUCTIVE SYSTEM. 



unites with the vas deferens to form the ejaculatory duct. Its 

 walls are similar in structure to those of the vas. It is lined 

 with columnar epithelium, which rests on a tunica propria, 

 beneath which is submucous areolar tissue. Its mucosa is 

 thrown into interlacing rugae and plications, which form sac- 

 cular and somewhat gland-like recesses ; the mucous coat also 

 contains small glands. Beneath the submucosa is an inner 

 circular and outer longitudinal layer of involuntary muscle, 

 outside of which is areolar tissue. 



The ejaculatory ducts, one on each side, are formed by the 

 union of the vasa deferentia with the outlets of the seminal 

 vesicles. They are situated partly within the prostate, and 

 empty into the prostatic urethra. They are lined with simple 

 columnar epithelium, resting on connective tissue ; outside the 

 latter are thin inner circular and outer longitudinal layers of 

 involuntary muscle. 



The prostate gland is a compound tubular gland, the mu- 

 cous secretion of which enters into the composition of the 

 semen. It surrounds a portion of the urethra and ejaculatory 

 ducts. It is made up of sustentacular connective tissue, invol- 

 untary muscle, and secreting alveoli, besides vessels and nerves. 



The sustentacular connective tissue consists of a firm fibrous 

 capsule, septa traversing the organ in various directions, and 

 interalveolar tissue. Intermingled with and accompanying 

 the connective tissue throughout the organ, forming in many 

 places the greatest part of its framework, is a large amount 

 of involuntary muscle, in the capsule and septa, between the 

 alveoli, and surrounding the urethra. 



The glandular alveoli of the prostate are of a racemose or 

 compound tubular character, and are lined with columnar 

 epithelium. 



Their ducts unite to form twelve to twenty outlet-ducts 

 opening into the urethra /. f., the " prostatic sinus" on each 

 side ; the epithelium lining the ducts merges into the squa- 

 mous type of the urethra. Many of the alveoli contain minute 

 round, concentrically marked calculous granules, or prostatic 

 concretions. From the lower surface of the urethra a short 

 small cul-de sac extends into the prostate ; this is called the 

 sinus pocularis or uterm masculinus, and is homologous to the 

 female uterus. 



