372 THE ABDOMEN AND PELVIS 



that interference with the rectum or anal canal produces 

 reflex results in the bladder. For example, retention of urine, 

 due to spasm of the sphincter vesicse internus, may follow 

 operations on the anus or rectum. A similar result may be 

 brought about by irritation of the cutaneous nerves of the 

 perineum (S. 2, 3, and 4), e.g. following a long cycle ride. 



Cutaneous branches are supplied by S. 2 and 3 to the back 

 of the thigh and leg (p. 418), and may be the site of referred 

 pain in irritative or inflammatory conditions of the rectum or 

 pelvic colon. 



The lower part of the anal canal, which is ectodermal in 

 origin (p. 381), receives its nerve -supply from the inferior 

 haemorrhoidal nerve. 



The Lymph Vessels of the rectum and anal canal, above 

 the pectinate line, drain into lymph glands which lie on the 

 posterior surface of the rectum and their efferents ascend along 

 the superior hsemorrhoidal artery to end in the sacral and 

 lumbar lymph glands. 



From the lower part of the anal canal, the lymph vessels 

 pass to the subinguinal lymph glands (p. 400). They reach their 

 destination by two paths ; some run antero-laterally across 

 the urogenital triangle, and the others run postero-laterally 

 round the lateral aspect of the thigh at about the level of the 

 greater trochanter. From the inguinal group, efferents pass 

 through the femoral (crural) ring to join the external iliac lymph 

 glands. 



Examination of the Rectum and Anal Canal. After 

 passing through the anus, the finger is at once grasped by the 

 external sphincter, but may be gently advanced upwards and 

 forwards for about one and a half inches, until it slips past 

 the internal sphincter and enters the rectal ampulla. If the 

 anus is found to be tightly contracted and very tender, anal 

 fissure may be suspected, and further examination should be 

 conducted under an anaesthetic. 



Through the lowest part of the anterior wall of the rectal 

 ampulla the bulbo-urethral glands (of Cowper) can be felt, when 

 they are inflamed and enlarged. At a slightly higher level, 

 the posterior surface of the prostate can be examined. The 

 seminal vesicles, lying on the posterior surface of the bladder, 

 can be recognised, when diseased, as nodular projections im- 

 mediately above the prostate. About three inches from the 

 anus, which is the average limit of reach, the finger-tip is in 



