The Perineum. 287 



ligament and transversus perinei muscle; internally, by 

 the obliquely directed levator ani and the coccygeus mus- 

 cles ; externally, by the obturator fascia covering the obtu- 

 rator muscle and by the ischium, and behind these, by the 

 gluteus maximus muscle and the great sacro-sciatic liga- 

 ment. The ischio-rectal fossa contains areolar tissue 

 with the inferior hemorrhoidal vessels and nerves running 

 obliquely through it, towards the rectum, while super- 

 ficially, the perineal vessels and nerve run forwards, and 

 posteriorly, the branch from the fourth sacral nerve passes 

 to the external sphincter. 



Pelvic Fasciae. The obturator layer of the pelvic 

 fascia is attached, above, to the pectineal line and passes 

 downwards, covering the obturator muscle. But, at the 

 level of the line joining the spine of the ischium with the 

 back of the symphysis, it is thickened, forming what is 

 known as the white line of the pelvic fascia. The lateral 

 portion of the levator ani arises from this white line, and 

 at the line, the obturator fascia splits into three layers, 

 viz., one, that continues the course of the original layer, 

 and, still covering the obturator muscle, forms the outer 

 wall of the ischio-rectal fossa; a second, that is directed 

 downwards towards the anus lying beneath the levator 

 ani muscle, and, therefore, forming the inner wall of the 

 ischio-rectal fossa ; while a third passe down towards the 

 median line of the pelvis, above the same muscle, and, 

 since the pelvic viscera and the prostate gland lie above 

 the levator ani muscle, this layer of fascia the recto- 

 vesical surrounds the prostate gland and the lower parts 

 of these viscera, and thus separates them from each other. 



The Penis is composed of two corpora cavernosa 

 and the corpus spongiosum, enveloped in a fibrous sheath 

 the tunica albuginea. The two corpora cavernosa are 

 separated behind where they form the crura, but lie, side 



