STRUCTURE OF THE URETHRA. 



307 



at different points, since its external boundary cannot be 

 exactly determined; its vessels and muscles being gradually 

 continuous with those of the corpus cavernosum. At the 

 root of the penis its thickness is about 0'178 of a millime- 

 ter, but more anteriorly it is thinner, not exceeding 0'13 of a 

 millimeter. 



Fig. 215. 



Fig. 215. Transverse section through the urethra (pars cavernosa) 

 of a Child, a, epithelium ; 6, mucosa ; c, muscular trabeculae ; d, 

 blood cavities of the corpus cavernosum ; e, glands ; /, excretory duct 

 of the glands ; g, longitudinal muscles ; h, albuginea. As seen with 

 Hartnack's objective system No. 2, ocular 3. 



The papillse of the mucous membrane which project into the 

 deep surface of the epithelium are only numerous and strongly 

 developed where the latter is laminated and tesselated. Where 

 it is of the transitional form, the papillse are short, and few in' 

 number. They attain their greatest length on the lower wall 

 of the fossa navicularis and towards the orificium urethrae, 

 where they are as long as 0'14 of a millimeter. All the papillae 



x2 



