388 The Rectum 



sacral nerves. Then there may be great pain in the back and along the 

 peripheral branches of the sacral plexus. In most cases there is a sense 

 of fulness of the lower bowel, on account of pressure upon its sensory 

 nerves, and, therefore, a frequent desire for evacuation. The motions 

 are often small and liquid, the solid part remaining behind as a harden- 

 ing mass. The sphincter is usually dilated. If the disease is too far 

 advanced for excision to be undertaken, comfort may be obtained and 

 life prolonged by diverting the faeces through an artificial anus in the 

 groin or loin. 



Arteries. The inferior mesenteric of the abdominal aorta lies 

 behind the upper part of the rectum (superior hccuwrrhoidal], and 

 then divides into a trunk for either side of the bowel. Branches are 

 thence given off which pierce the muscular coat and run in the sub- 

 mucous layer almost to the anus, anastomosing with those next de- 

 scribed. The middle hcemorrhoidah are derived from the internal 

 iliacs ; branches also come from the lower vesical and sacral, and from 

 the internal pudics within the pelvis ; they communicate with each 

 other and with the superior and inferior haemorrhoidals. The inferior 

 or external hamotYhoidal arteries come from the internal pudics in 

 the ischio-rectal fossa (p. 442). They anastomose with each other and 

 with the higher haemorrhoidal arteries. Their branches are divided 

 in lateral lithotomy, and also in the operation for anal fistula. 



Veins. The haemorrhoidal plexus is found in the lower part of the 

 rectum, in the mucous and submucous coats. It communicates with 

 the veins of the neck of the bladder and prostate. The branches are 

 destitute of valves, and the chief of them enter into the inferior mesen- 

 teric vein which ends in the splenic, itself an important tributary of the 

 vena portae (p. 338) ; others flow into the internal iliac and internal pudic 

 veins. Thus a noticeable communication is effected between the portal 

 and systemic circulation. 



Piles are varicose haemorrhoidal veins ; when prolapsed from the 

 interior of the bowel they are covered with mucous membrane and are 

 apt to bleed ; external piles are tumours of the inferior haemorrhoidal 

 veins, and, possessing a thick (dermal) coating, they do not bleed. A 

 branch of a haemorrhoidal artery descends into the base of the internal 

 pile ; the pendulous tumour must therefore not be cut off unless this 

 vessel is first secured, either by a clamp or ligature. In freeing the 

 base of the pile for ligation the blades of the scissors must be passed 

 up parallel to the wall of the rectum, and between it and the pile. Any 

 condition which obstructs the return of the venous blood predisposes 

 to dilatation of these veins. Piles may, therefore, be symptomatic of 

 disease of the heart, lungs, or liver ; of stricture of the rectum ; of 

 habitual constipation, pregnancy, ovarian disease or abdominal tumour ; 

 of prostatic enlargement, or of vesical calculus. 



The nerves of the rectum are derived chiefly from the inferior 

 mesenteric derivatives of the aortic plexus, and from the hypogastric 



