310 SPLANCHNOLOGY. 



stomach. From this flexure proceeds the fourth and last part of 

 the large colon, which passes backwards, and, at the level of the 

 base of the caecum, is constricted, and continued as the floating 

 colon. 



The attachments of the large colon are, at its origin, to the 

 caecum by the meso-caBcum, at its terminal portion by cellular 

 tissue to the pancreas and arch of the csecum, and by the meso- 

 colon, a double fold of peritoneum which unites the two halves 

 for some distance, enveloping the entire organ except at its 

 junction with other viscera, and attaching it to the sublumbar 

 portion of the abdominal wall. The diameter of the canal varies. 

 Very narrow at its origin, it abruptly enlarges, and its size then 

 remains much the same as far as the pelvic flexure, where it 

 contracts ; the third division is comparatively small, but at the 

 third flexure it again expands, the fourth division being the 

 largest of all ; it is finally constricted, as it forms the origin of 

 the floating colon. Externally, it has numerous transverse furrows 

 and longitudinal muscular bands ; the latter vary in number ; as 

 far as the pelvic flexure, there are four ; along the narrow third 

 portion, only one ; at the third flexure, again three, which persist, 

 two being continued along the floating colon. The internal 

 surface resembles that of the caecum. 



FLOATING COLON. 



The single or floating colon succeeds the great colon, and is 

 convoluted, like the small intestines, but is twice as large, in 

 length averaging about ten feet, and regularly crumpled by trans- 

 verse folds and longitudinal muscular bands. The latter are two 

 in number, one on the greater or convex, the other on the lesser 

 or concave curvature. It leaves the large colon to the left of the 

 cascum, in close relation with the termination of the duodenum. 

 It principally occupies the left flank or lumbar region, its con- 

 volutions mixing with those of the small intestine, and near the 

 anterior part of the pelvis it terminates in the rectum. Floating 

 like the small intestine, it is suspended by the colic mesentery, 

 which is larger than, but resembles in structure that of, the small 

 intestine. 



RECTUM. 



The rectum, or straight intestine, extends in a direct line from 

 the entrance of the pelvic cavity to the anus, and resembles iu 



