THE PERINEUM 383 



rectum and anal canal. In such operations the pelvic colon is 

 mobilised (p. 343) so as to permit of its being stitched to the 

 anus, and, at the same time, the external sphincter is preserved. 



The Male Urethra is about nine inches long from its 

 internal orifice at the neck of the bladder to its external orifice 

 on the glans penis. It may be conveniently divided into a 

 posterior, fixed portion, consisting of the prostatic and 

 membranous parts and the part within the bulb and an anterior, 

 movable portion, situated in the corpus cavernosum urethrae 

 (corpus spongiosum). 



In the flaccid condition of the penis, the urethra follows an 

 c/) -shaped bend, but when the penis is drawn upwards towards 

 the abdomen, its course becomes J-shaped. By this alteration, 

 the surgeon is enabled to pass a rigid instrument with a single 

 curve along the urethra into the bladder. 



The Prostatic Part of the Urethra is about ij inches 

 in length and is embedded in the prostate, somewhat nearer 

 to the anterior than to the posterior surface. It is the widest 

 and also the most dilatable part of the urethra. About half 

 an inch wide at its mid-point, it narrows slightly at each end, 

 but it may be dilated so as to permit the passage of the finger 

 into the bladder. On account of this distensibility, the removal 

 of stones from the bladder was at one time carried out through 

 the prostatic urethra. 



A longitudinal ridge, termed the urethral crest, occupies the 

 floor of the prostatic urethra in nearly its whole extent. 

 Longitudinal grooves lie one on each side of the crest ; they are 

 termed the prostatic sinuses and receive the prostatic ducts. 

 It is in these ducts that chronic gonorrhceal inflammation may 

 linger in posterior urethritis. Near the lower end of the crest, 

 a small median opening leads into a blind diverticulum, which 

 passes upwards and backwards below the middle lobe of the 

 prostate. This is termed the prostatic utricle (sinus pocularis), 

 and near its orifice, which is sometimes large enough to entangle 

 the point of a fine instrument, the prostatic urethra receives 

 the openings of the ejaculatory ducts. Gonorrhceal infection 

 of the posterior urethra may spread into the ejaculatory ducts 

 and involve the seminal vesicles, or it may spread along the 

 ductus (vas) deferens and give rise to epididymitis. 



The Membranous Part of the Urethra is narrower than 

 any other part of the urethra except the external orifice. It 

 is only three-quarters of an inch long, and it lies between the 



