254 ELEMENTS OF HISTOLOGY. [Chap. xxxi. 



epithelium of the pars prostatica of the urethra 

 passes a short distance into the duct. 



The alveoli are surrounded by dense networks of 

 capillary blood-vessels. 



In the peripheral portion of the gland numerous 

 ganglia are interposed in the rich plexus of nerves. 

 Also Pacinian corpuscles are to be met with. 



337. (5) The urethra.. The mucous membrane 

 of the male urethra is lined with simple columnar 

 epithelium, except at the commencement the pars 

 prostatica and at the end the fossa navicularis 

 where it is stratified pavement epithelium. 



The mucous membrane is fibrous tissue with very 

 numerous elastic fibres. Outside of it is a muscular coat 

 composed of non-striped muscular tissue, and arranged 

 as an inner circular and an outer longitudinal stratum, 

 except in the pars prostatica and pars membranacea, 

 where it is chiefly longitudinal. In the latter portion 

 the muscular bundles pass also into the mucous mem- 

 brane, where they follow a longitudinal course between 

 large veins arranged in a longitudinal plexus. These 

 veins empty themselves into small veins outside. This 

 plexus of large veins with the muscular tissue between 

 represents a rudiment of a cavernous tissue (Henle). 



The mucous membrane forms peculiar folds sur- 

 rounding the lacunse Morgagni. There are small mucous 

 glands, lined with columnar epithelium, embedded in 

 the mucous membrane ; they open into the cavity of 

 the urethra and are known as Littre's glands. 



338. (6) The glands of Cowper. Each gland 

 of Cowper is a large compound tubular gland, which, 

 as regards structure of ducts and alveoli, resembles a 

 mucous gland. The wall of the chief ducts possesses 

 a large amount of longitudinally-arranged non-striped 

 muscular tissue. The epithelium lining the ducts is 

 composed of columnar cells. The alveoli possess a 

 large lumen and are lined with columnar mucous 



