CHAP. XXXVII.] URETHRA. 543 



supposed ; the minute terminal vessels ultimately open into the 



venous spaces. The arrangement of Fig. 259. 



the arteries in the corpus spongio- 



sum urethrse, is similar to that just 



described. 



Urethra. The male urethra is the 

 canal which extends from the neck 

 of the bladder to the end of the 

 penis. It is about eight inches and 

 a half in length, but varies slightly 

 in different cases. The tube itself is 



lined with mUCOUS membrane, and A small artery of the corpora cavernosa. 

 ] , , i giving off a lateral branch, from which proceed 



its diameter IS not by any means helicine arteries, terminating in very small 

 ,1 - -i i , , T , vessels, which are continued in the trabecular 



the Same in its Whole extent. ItS tissue (.) b. Wall of the arteries. After 



direction is that of a double curve, K 



like the letter f. The walls of the urethra are strong, and com- 

 posed principally of fibrous tissue, with a layer of unstriped mus- 

 cular fibre, the arrangement of which has been well described by 

 Mr. Hancock. 



The urethra is divided, by descriptive anatomists, into three 

 portions ; the prostatic, being about twelve lines long ; the mem- 

 branous, about three-quarters of an inch in length in its upper part 

 but only half an inch in its lower portion; and the remainder, by 

 far the most extensive portion of the canal, called the spongy por- 

 tion^ which reaches to the orifice. 



The prostatic portion of the urethra is its widest part, and lies 

 imbedded in the upper part of the prostate, above its middle lobe. 



At the neck of the bladder, the mucous membrane forms a fold, 

 called the uvula vesicce. Anterior to this is a narrow ridge, rising 

 from the floor of the tube, about nine lines in length, and about 

 one and a half lines in height in its highest part, called the veru- 

 montanum, caput gallinaginis, or crest of the urethra.* On each side 

 of this, the mucous membrane forms a depression, the prostatic 

 sinus, into which the ducts of the prostate gland open. 



At the highest part of the verumontanum is a little sinus, the 

 vesicula prostatica. It is here that the ejaculatory ducts open. 



The membranous portion is that narrowest part of the urethra 

 which lies beneath the pubis and passes through the layers of the 

 triangular ligament. It is surrounded with muscular fibres, and 

 the compressor urethrce muscle is situated upon this part of the tube ; 



* Vide article " Vesicula Prostatica," in the Cyclopaedia of Anatomy and 

 Physiology, by Prof. Rud. Leuckart. 



