MUSCULAR COAT. 387 



the transverse colon, are found a number of little sacculated 

 pouches filled with fat, called the appendices epiploicse. 

 The sigmoid flexure of the colon is invested with peritoneum, 

 except at the attachment of the iliac mesocolon. This divi- 

 sion ,,of the intestine is capable of considerable motion. The 

 upper part of the rectum is almost completely covered by 

 peritoneum, and is but loosely held in place. The middle 

 portion is closely bound down, and is only covered with peri- 

 toneum anteriorly and laterally. The lowest portion of the 

 rectum has no peritoneal covering. 



Muscular Coat. The muscular fibres of the large intes- 

 tine have an arrangement quite different from that which 

 exists in the small intestine. The external, longitudinal 

 layer, instead of extending over the whole tube, is arranged 

 in three distinct bands, which commence in the caecum at 

 the vermiform appendix. Passing along the ascending co- 

 lon, one of the bands is situated anteriorly, and the others 

 latero-posteriorly. On the transverse colon, the anterior band 

 becomes inferior, and the two latero-posterior bands become 

 respectively postero-superior and postero-inferior. On the de- 

 scending colon and the sigmoid flexure, the muscular bands 

 resume the relative position which they had on the ascending 

 colon. As these longitudinal fibres pass to the rectum, the 

 anterior and the external bands unite to pass down on the 

 anterior surface of the canal, while the posterior band passes 

 down on its posterior surface. Thus the three bands are here 

 formed into two. These two bands as they pass downward, 

 though remaining distinct, become much wider ; and longitu- 

 dinal muscular fibres commencing at the rectum are situated 

 between them, so that this part of the canal, especially in its 

 lower portion, is covered with longitudinal fibres in a pretty 

 uniform layer. 



The termimation of the muscular fibres of the rectum has 

 been closely studied by Sappey. He has found that as far 

 as their terminations are concerned, the fibres may be divided 



