THE PERINEUM 373 



contact with the rectal wall just below the line of peritoneal 

 reflection. 



If the finger is rotated laterally, the medial aspect of the 

 pelvic wall may be examined, and, posterp-laterally, the hypo- 

 gastric (internal iliac) lymph glands can be made out when 

 they are enlarged. 



With the pulp of the finger directed backwards, the lowest 

 plica transversal-is recti (rectal valve) may be felt, and enlarged 

 lymph glands on the anterior surface of the sacrum can be 

 recognised by pressing them against the bone. When the 

 patient is told to strain, the part of the bowel which lies just 

 out of reach in the passive condition can be " threaded " on 

 the finger and examined. 



In the " ballooned " condition of the rectum, the walls of 

 the gut cannot be made out after the finger has passed through 

 the internal sphincter. 



In the female, the os uteri can be palpated through the 

 anterior wall of the rectum, and the uterus itself may be felt 

 when retroflexed. 



THE PERINEUM. 



The Ischio-Rectal Fossa lies between the lower part of 

 the obturator internus and the levator ani. Posteriorly, it is 

 limited by the glutseus maximus and the sacro-tuberous ligament; 

 anteriorly, it extends forwards to the urogenital diaphragm. 

 Above, it is shut off from the pelvis by the attachment of the 

 levator ani to the parietal pelvic fascia (Fig. 114). The sloping 

 medial wall of the fossa is formed by the levator ani as it clothes 

 the anal canal and the lower part of the rectum. 



After leaving the gluteal region (p. 417), the internal pudendal 

 vessels enter Alcock's canal, which lies in the fascia on the 

 lateral wall of the ischio-rectal fossa. They give off the inferior 

 hsemorrhoidal vessels, which pass downwards and medially 

 across the fossa to supply the anal canal. The vessels are 

 accompanied by the inferior hsemorrhoidal nerve, which arises 

 from the pudendal and terminates in the external sphincter. 



Ischio - rectal abscesses originating in connection with 

 some small ulcer, laceration of the rectal sinuses, etc., may 

 rupture through the skin and give rise to an external sinus ; or 



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