THE LARGE INTESTINE. 377 



descending colon, which is covered anteriorly and at the 

 sides by peritoneum, and terminates in the convolutions 

 of the colon called the sigmoid flexure, which is held in 

 position by the sigmoid meso-colon. It terminates in the 

 rectum, which is a cylinder about eight inches long. It 

 begins at the left side of the lumbo-sacral articulation, 

 curves slightly to the right, then follows the curve of the 

 sacrum, and finally bends abruptly backward to termi- 

 nate at the anus. It is divided into an upper, middle, 

 and inferior portion. The upper part is about three and 

 one-half inches long, passes downward to the upper bor- 

 der of the third piece of the sacrum. It is invested by 

 peritoneum and held in place by the meso-rectum. The 

 middle part, about three inches long, terminates on a 

 level with the tip of the coccyx. The lower portion 

 extends from the tip of the coccyx to the anus, and is 

 about one and a half inches long. It is encircled by 

 the internal sphincter and forms the posterior limit to the 

 perineum. The large intestine has four coats, serous, 

 muscular, cellular, and mucous. The serous coat is 

 formed by the peritoneum. It covers the anterior sur- 

 face and sides of the caecum, ascending colon, and de- 

 scending colon. It entirely invests the transverse colon, 

 the sigmoid flexure, and the first or upper part of the 

 rectum. The muscular coat consists of longitudinal and 

 circular fibres. The longitudinal fibres are collected into 

 three bands about half an inch in width. They are only 

 about three-fifths as long as the large intestine, and by 

 their attachment to the sides of the gut cause the saccu- 

 lation or pouching. The fibres of the bands become 

 diffused on the surface of the sigmoid flexure. They are 

 placed nearly equidistant, and generally are arranged, 

 one anteriorly, one along the inner side, and one along 

 the outer side of the colon. The circular fibres form a 



