1038 



THE ORGANS OF DIGESTION. 



The rectum constitutes the terminal portion of the intestinal tube. It received 

 its name intestinum rectum from its straight course in animals. In the human 

 subject its course is nearly vertical, but it presents four curves and should be 

 called intestinum curvum (Lisfranc). 



The ancient and much-copied method of description divides it into three 

 parts. We hesitate to introduce a change in old nomenclature, but will mention 

 those proposed and allow the reader to make his choice. 



Treves in 1885 called attention to the fact that there Avas no demarcation be- 

 tween the sigmoid flexure and the first part of the rectum at the brim of the pelvis. 

 So he concludes the intestines should be called sigmoid flexure until the mesocolon 

 is lost, i. e. until it reaches the third sacral vertebra. This rectum, therefore, 

 has the two lower parts of the three usually described and no inesorectum. Cun- 

 ningham and Quain take for the rectum the upper two of the three usually 

 described, the third being regarded as a separate part called anal canal. 



The rectum in three parts is situated in the pelvic cavity and on its floor. It 

 is attached to its posterior wall, whose curve it follows. Its inferior limit is a 



circular line separating the skin 

 from the mucous membrane the 

 anal orifice. Its superior limit can- 

 not be determined precisely ; it is 

 continuous with the sigmoid flexure, 

 but there is only an arbitrary line 

 of demarcation. This is the pelvic 

 brim, most usually opposite the left 

 sacro-iliac articulation, quite often 

 the sacro-vertebral angle, or rarely 

 on the right of the base of the 

 sacrum. Superiorly, it is united to 

 the sacrum by a fold of peritoneum, 

 the mesorectum. Lower down the 

 peritoneum only covers the sides 

 and front, much as in the case of 

 the descending duodenum (Fig. 

 657). Still lower down, at a height 

 of about one inch above the prostate 

 gland, it entirely abandons the rec- 

 tum and is reflected upon the neigh- 

 boring organs, making, according to 

 sex, the recto-vesical pouch or the 

 recto-vaginal and recto-uterine. The 

 height of the recto-vesical pouch in 

 the male is never more than 8 cm. 

 above the anus. The height of the 

 recto-vaginal in the female is always 

 less, about 6 cm. The length of the 

 rectum, measured along its anterior 

 wall (in the body), is 18 to 22 cm., 

 or about eight inches. Outside the 



FIG. 657. Relations of peritoneum to rectum and bladder, i i , or mr. 7-1 



Outline of rectum. (Tiiiaux.) body it measures z5 cm. Ihe calibre 



varies according to circumstances. 



When empty it is less than that of the other portions of the large intestine. 

 When it contains a certain amount of faecal matter its middle portion is more or 

 less dilated, but not to the size of the caecum. The calibre of the remainder, in 

 general, is not circular. In the lower part of the rectum it presents a transverse 

 slit, and the anterior and posterior walls lie upon each other, mainly from the 

 pressure of the anterior organs forcing the rectum back on the sacrum and 

 coccyx. Just at the turn of the rectum into its third portion, and especially 



