THE PENIS. 659 



proceeds to the symphysis pubis, beneath which it makei 

 a slight curve, having the concavity upward. 



This portion is called the membranous, while the balance, 

 commencing at the bulb and going to the extremity of the 

 glans, receives the name of the spongy portion. 



The length of the urethra varies according to the erection 

 of the penis, averaging from seven to nine inches. To the 

 prostatic portion is given about an inch and a half, and to 

 the membranous about an inch. The urethra is composed 

 of two coats, an outer fibrous and elastic, and varying in 

 strength and density at different points, being stronger in 

 the prostatic and membranous portions than in the spongy; 

 and the inner or mucous coat which is smooth and thin, 

 and continuous with the mucous coat of the bladder poste- 

 tiorly, and the integument of the glans anteriorly, also 

 with the lining membrane of the excretory ducts of Cow- 

 per's glands, the prostate, the ejaculatory ducts, and the 

 several lacunae. 



The prostatic portion is considered the widest part of the 

 canal ; on its lower surface the mucous coat presents a lon- 

 gitudinal fold along the mesial line, called caput gallinagi- 

 nis or verumontanum. On each side of the caput gallinaginis 

 a fossa is seen, called prostatic sinus, in which the ducts of 

 the prostate open. At the anterior extremity of the caput 

 the common ejaculatory ducts are found to terminate, and 

 between the latter, an opening looking backward into a 

 small dilated sac, is noticed, called sinus pocularis. The 

 caput gallinaginis is regarded in the light of a valve to 

 prevent the escape of urine in the contracted state of the 

 urethra ; but during the action of the detrusor urinse, the 

 caput is drawn down and the elastic ring expanded so as 

 to permit the escape of the urine. The membranous portion, 

 is the narrowest part of the canal, and is surrounded by an 

 elastic and erectile reddish tissue, and the deep layer of the 

 triangular ligament,with the compressores urethrae muscles 

 It lies between the prostate and bulb. In the latter the 

 urethra again enlarges, and then again in the spongy por- 

 tion, which is the longest of the three, becomes smaller till 



