THE REPRODUCTIVE ORGANS. 755 



Structure. (a.) The urethra is lined by stratified pavement epithe- 

 lium in the prostatic portion; in front of the bulb the epithelium 

 becomes columnar, while at the fossa navicularis it is again lined 

 with stratified pavement epithelium. The mucous membrane consists 

 chiefly of fibrous connective-tissue, intermixed with which are many elastic 

 fibres. It is surrounded by unstriped muscular tissue. In the inter- 



Fig. 452. Erectile tissue of the human penis, a, fibrous trabeculae with their ordinary 

 capillaries; 6, section of the venous sinuses; c, muscular tissue. (Cadiat.) 



mediate portion many large veins run amongst the bundles of muscular 

 tissue. Many mucous glands, glands of Littre^ are present. 



(b.) The corpora cavernosa, a true erectile structure, are surrounded 

 by a dense fibrous and elastic sheath, and from the inner surface of this, 

 and from the septum which separates the two corpora cavernosa, pass 

 numerous bundles of fibrous, elastic, and plain muscular fibres, called 

 trabeculce, and these by their anastomosis form a series of irregular 

 spaces. These spaces are lined with endothelium, and are filled with 

 venous blood. The inter-trabecular spaces or sinuses of one corpus 

 cavernosum anastomose with those of the other, especially in front where 

 the dividing septum is incomplete. 



(c.) The corpus spongiosum urethrse consists of an inner portion or 

 plexus of longitudinal veins, and of an outer or realty cavernous portion 

 identical in structure with that which has just been described. The 

 lymphatics of the penis are very numerous, both superficially and also 

 around the urethra. They join the inguinal glands. 



The nerves, derived from the pudic nerves and hypogastric plexus, 

 are distributed to the skin and mucous membrane and to the corpora 

 cavernosa and spongiosum respectively. The nerves are provided with 

 end bulbs and Pacinian corpuscles in the glans penis, and form also a 

 dense subepithelial plexus. 



Cowper's glands are two small glands, the ducts of which open into 



