236 ANATOMY OF THE ABDOMEN. 



always furnished with water, for soHd ingesta as well as 

 fluid is found within it. 



The colon originates from the csecum in the right hypo- 

 chondriac, whence it reaches across the abdomen into the 

 left iliac ; though this end floating free has no absolutely 

 fixed position. Having reached the left side it makes its 

 sigmoid flexure, or bends upon itself to proceed back again, 

 and so terminate in the right hypochondriac, where the 

 continuation of the intestine assumes the name of the rec- 

 tum. It is connected one part to the other, that is, from 

 the csecum to the sigmoid flexure ; but it is perfectly free 

 at its other side, so that without destroying the integrity of 

 the pai'ts, the colon might trail upon the ground. It is of 

 different dimensions; thus after it has commenced it 

 enlargss, and towards its termination it takes on its greatest 

 magnitude, and at this place commonly loses its muscular 

 bands. 



The rectum is the continuation of the colon, and passes 

 backwards under the lumbar region to the anus. Its sub- 

 stance is thicker than that of the other intestines ; and 

 has a longitudinal muscular band upon its either side ; by 

 these it is puckered into cell-like depressions, to prevent a 

 too frequent expulsion of the faeces. The rectum is rather 

 loosely suspended from the spine and sacrum by a detachment 

 of :he peritoneum, which is here called mesocolon: yet 

 the peritoneum does not invest the whole of the rectum, but 

 lea\es it as it approaches its termination ; the place of the 

 pertoneum being supplied by cellular membrane. The 

 anu\ is opened by the force of the peristaltic motion, and is 

 shul by a muscular band around the extremity of the gut, 

 calhd the sphincter ani. 



%e mesentery and mesocolon. — These great folds of 

 menbrane are simply prolongations of the peritoneum, 

 witlin the turn of which the intestines are enclosed : these 

 inveting folds, uniting at the superior part, form appa- 

 rently a single membrane, called mesentery, and which con- 

 seqiently has two smooth surfaces. Such peritoneal pro- 

 longations are very useful ; for they not only invest the 

 intetines, and give them their outer covering, but they in 

 some measure keep them within their situations, and fur- 

 nisl a medium through which they receive their blood- 



