THE PERINEUM. 453 



and membranous urethra. The artery of the bulb is a 

 short branch of the internal pudic ; it is distributed to the 

 bulb. The internal pudic artery runs along the ascending 

 ramus of the ischium, and gives off the artery to the 

 corpus cavernosum. Cowper's gland is a small, yellow, 

 lobular mass, about the size of a pea ; its duct opens into 

 the bulb of the urethra. The membranous urethra is 

 that portion of the canal between the superficial and 

 deep layers of the deep perineal fasciae ; removal of the 

 deep layer of the deep perineal fascia exhibits the pros- 

 tate and lower portion of the bladder. 



The ischio-rectal region comprises that portion of the 

 perineum behind the transversus perinei muscles ; it pre- 

 sents at the centre the anal opening, surrounded by a 

 superficial stratum of muscular fibres, the external 

 sphincter. On either side of the rectum is a conoidal 

 space filled with fat ; traversing the space are the super- 

 ficial haemorrhoidal vessels and nerves. When the fat 

 is removed it brings into view the levator ani muscle, 

 which supports the pelvic organs. 



In the female the perineum consists of some of the 

 external genitalia (already described, page 403) and 

 the following modifications : The urethra, which opens 

 between the labia minora, at the bottom of the vestibule, 

 is a short canal three-fourths of an inch long ; in fact, 

 simply a membranous urethra imbedded in the anterior 

 wall of the vagina. The opening of the vagina is 

 guarded in the virgin state by the hymen, which is, in fact, 

 a thin, incomplete prolongation of the superficial layer of 

 the deep perineal fascia, lined by mucous membrane. 

 The orifice* of the vagina is surrounded by a superficial, 

 flat, sphincter muscle, continuous with the superficial 

 sphincter of the rectum. The perineum proper is that 

 wedge-shaped mass of tissue between the vagina and 



