THE LARGE INTESTINE. 573 



having a diameter of two or three lines, is composed of 

 similar structures with the rest of the intestine, and com- 

 municates with the coecum by a somewhat valvular ar- 

 rangement. The use of this appendix is unknown. 



The coecum is joined on its left side, at an acute angle, 

 by the ilium. The ilium seems to perforate the coecum, 

 and at its point of entrance presents a transverse elliptical 

 slit about an inch in length, (Fig. 184, A,) having access- 

 ory fibres called retinacula, to strengthen its extremities. 

 The sides of this slit constitute folds or valves ; the inferior 

 or ilio-coecal, and the superior or ilio-colic valve. The for- 

 mer prevents regurgitation from the coecum, and the latter 

 from the colon into the ilium. This valve consists of two 

 layers of mucous tissue investing cellular and muscular 

 fibres, and is formed by the mucous coat and circular fibres 

 of the ilium protruding through a separation in the circu- 

 lar fibres of the ccecum. It looks downward. 



The colon (Fig. 185) is a continuation of the coecum up- 

 ward, and is divided into the ascending, transverse, descend- 

 ing, and sigmoid flexure. Its course and connections have 

 already, to some extent, been given ; and it may be further 

 added that the ascending colon passes in front of the right 

 kidney, bordering the duodenum on the left, to the under 

 surface of the liver, where, by its connection with the gall- 

 bladder, it is frequently tinged with bile ; thence it makes 

 its arch (transverse colon) across the abdomen, being bounded 

 above by the stomach, and below by the small intestine. 

 On the left it descends, being hid by the small intestine in 

 front, and resting upon the kidney, it terminates in the left 

 iliac region by a curve which goes first upward, then by 

 one or more coils downward, to the sacro-iliac symphysis, 

 where it ends in the rectum. This curve is called the sig- 

 moid flexure. It is covered by a reflection of the peritoneum, 

 allowing it frequently to be quite loose, and giving it con- 

 siderable motion. 



The rectum, (Fig. 185,) so called from its straight course, 

 is not so, strictly speaking, for commencing at the left ilio- 

 sacral articulation, where the sigmoid flexure terminates, 



