856 THE INTESTINE. 



to bo marked all over by the orifices of numerous tubuli, resembling those 

 of the stomach and the crypts of the small intestine. These follicles are 

 arranged perpendicularly to the surface of the membrane ; they are longer 

 and more numerous, and are placed more closely together and at more 

 regular intervals than those of the small intestine. Their orifices are cir- 

 cular, and, when widened by the loss of their epithelial lining, they give the 

 mucous membrane a cribriform aspect. 



Besides these, there are scattered over the surface of the whole large 

 intestine numerous closed follicles, similar to the solitary glands of the small 

 intestine, but marked by a depression passing down to them between the 

 surrounding tubules (Kolliker). They are most abundant in the cgecum and 

 in its vermiform appendix ; being placed closely all over the latter. 



The epithelium, which covers the general surface of the mucous membrane, 

 and lines the tubuli and follicles, is of the columnar kind. 



Vessels and Nerves. In the great intestine of the rabbit, Frey figures the same 

 arrangement of capillary plexuses and venous radicles as has been described in the 

 stomach. He finds also in the rabbit clavate lacteals in rudimentary villi. (Zeitsch. 

 f. Wissensch. Zoologie, vol. xii.) ; but Teichmann's injections in the human subject 

 show no absorbents more superficial than the bases of the tubular follicles. 



Nervous plexuses similar to those of the small intestine have also been found in the 

 walls of the large intestine. 



THE RECTUM. 



The lowest portion of the large intestine, named the rectum, extends from 

 the sigmoid flexure of the colon to the anus, and is situated entirely within 

 the true pelvis, in its back part. 



Commencing opposite to the left sacro-iliac articulation, it is directed at 

 first obliquely downwards, and from left to right, to gain the middle line of 

 the sacrum. It then changes its direction, and curves forwards in front of 

 the lower part of the sacrum and the coccyx, and behind the bladder, 

 vesiciilae seminales and prostate in the male, and at the back of the cervix 

 uteri and vagina in the female. Opposite to the prostate it makes another 

 turn, and inclines downwards and backwards to reach the anus. The 

 intestinum rectum, therefore, so called from its original description being 

 derived from animals, is far from being straight in the human subject. Seen 

 from the front, the upper part of the rectum presents a lateral inclination 

 from the left to the median line of the pelvis, sometimes passing beyond 

 the middle to the right ; and when viewed from the side it offers two 

 curves, one corresponding with the hollow front of the sacrum and coccyx, 

 and the other at the lower end of the bowel, forming a shorter turn in the 

 opposite direction. 



Unlike the rest of the large intestine, the rectum is not sacculated, but is 

 smooth and cylindrical ; and it has no separate longitudinal bands upon it. 

 It is about six or eight inches in length ; and is rather narrower than the 

 sigmoid flexure at its upper end, but becomes dilated into a large ampulla or 

 reservoir, immediately above the anus. 



The upper part of the rectum is in contact in front with the back of tho 

 bladder (or uterus in the female), unless some convolutions of the small 

 intestine happen to descend into the interval between them. This part is 

 surrounded by peritoneum, which attaches it behind to the sacrum by a 

 duplicature named the meso-rectum. Lower down, the peritoneum covers 

 the intestine in front and at the sides, and at last its anterior surface only ; 



