58 POSITION OF THE RECTUM. 



posed of adipose membrane, varying in length from half an 

 inch to an inch and a half: these appear to be of the nature of 

 the omentum, and are therefore generally denominated Appen- 

 dices EpiploiccB. 



The Rectum. 



After forming the sigmoid flexure, the colon terminates ; and 

 the rectum begins opposite to the lower surface of the last 

 lumbar vertebra, and nearly in contact with it ; from this it 

 proceeds downwards, forming a curve like the sacrum, until it 

 terminates at the anus ; where it is invested with the muscles 

 called the sphincter and levator ani. It is called rectum, 

 because in this course it is supposed not to incline to either 

 side ; but it is often found on one side of the middle line.* 



This intestine being in contact with the posterior surface of 

 the pelvis, is covered, on its anterior surface only, by the perito- 

 neum which lines the posterior surface of the pelvis ; and it is 

 fixed in this situation by the peritoneum, as the colon is on the 

 right and left sides of the abdomen, but more loosely ; and, 

 therefore, the term Mesorectum has sometimes been applied to 

 that portion of the peritoneum which is analogous to the 

 mesentery and mesocolon. The peritoneum does not extend 

 to the end of the rectum ; for it is reflected at the lower part of 

 the pelvis from the rectum to the bladder, or uterus, and does 

 not line the bottom of the pelvis : so that the lower part of this 

 intestine, as well as that of the other viscera of the pelvis, is 

 below the peritoneum, and not connected with it. 



The muscular coat of the rectum is much thicker and 

 stronger than that of any other intestine. The strata of the lon- 

 gitudinal and circular fibres which compose it are very distinct 

 from each other. The longitudinal fibres are most numerous, 

 and terminate at the insertion of the fibres of the levator ani 

 muscle. 



The lower circular fibres are intimately connected with the 

 sphincter ani. 



* Morgagni and Haller supposed it to be commonly on the left of the middle 

 line, and Sabatier on the right. 



