PELVIS MINOR 



433 



symphysis. It lies therefore in the interval between these 

 two fasciae (Figs. 194, 199, 200). 



The mucous membrane of the membranous part of the 

 urethra is directly surrounded by a thin coat of erectile tissue, 

 and that is embraced by a muscular tunic composed of 

 involuntary fibres arranged circularly. 



Pars Cavernosa Urethrae (O.T. Spongy Portion of Urethra). 

 The cavernous portion is the longest division of the urethra. 



Ureter- 



Ductus deferens 



Seminal 

 vesicle 



Middle lobe _ 

 of prostate 



Utriculus prosta- 



ticus and - 

 ejaculatory duct 



Bulbo-urethral 



gland (Cowper's) 



Bulb of corpus 



cavernosum 



urethrae 



FIG. 203. Diagram of the Bladder, Urethra, and Penis. (D6le"pine. 



It is embedded in the substance of the corpus cavernosum 

 urethrae, and its calibre varies considerably at different points. 

 In each expansion of the corpus cavernosum urethrae, viz., the 

 bulb posteriorly and the glans anteriorly, there is a corre- 

 sponding dilatation of the urethra (Fig. 202); between the 

 dilatations the canal is of uniform diameter, and slightly wider 

 than the membranous portion? The dilatation of the urethra 

 in the glans is termed the fossa navicularis. At its orifice, 

 the external urethral orifice, the canal is much contracted, and 

 is even narrower than any part of the membranous portion, 

 VOL. II 28 



