438 ABDOMEN 



the large intestine. The chief points of difference are 

 (i) The wall of the small intestine is smooth and uniform, 

 whereas the wall of the large intestine is puckered and 

 sacculated. (2) The longitudinal muscle fibres in the wall of 

 the small intestine are distributed uniformly round the tube, 

 but in the large intestine they are collected into three 

 longitudinal bands, tanice. colt, which are separated from each 

 other by intervals and are distinctly visible to the naked eye. 

 These bands are shorter than the tube itself, consequently the 

 walls of the tube are puckered. (3) Attached to the great 

 intestine are the appendices epiploioE. These are small 

 peritoneal pouches, containing fat, which hang from the free 

 border of the gut. 



The dissector should attempt to pull the small intestine 

 forwards and he will find that it is attached to the posterior 

 wall of the abdomen by a fold of peritoneum called the 

 mesentery, which runs obliquely downwards and to the right, 

 from the level of the left side of the second lumbar vertebra 

 to the right iliac fossa. The parts of the large intestine lying 

 to the right of the mass of coils of small intestine are the 

 caecum below and the ascending colon above. The part 

 crossing from side to side, above the small intestine, now that 

 the great omentum is reversed, but which is normally in 

 front of the small intestine, is the transverse colon ; it is 

 attached to the posterior wall of the abdomen by a fold of 

 peritoneum called the transverse meso-colon. The parts to 

 the left of the coils of the small intestine are, from above 

 downwards, the descending colon in the lumbar region, and 

 the iliac colon in the left iliac region. The portion of the 

 small intestine which is attached to the posterior wall of the 

 abdomen by the mesentery is arbitrarily divided into two 

 parts, an upper two-fifths called jejunum (intestinum jejunum}, 

 and a lower three-fifths called ileum (intestinum ileum}. Pull 

 the jejunum and ileum downwards and to the left and follow 

 the mesentery to its highest point, where the jejunum will be 

 found to become continuous at a distinct flexure, the duodeno- 

 jejunal flexure, with a portion of the small intestine which is 

 not enclosed in the mesentery but which lies behind the 

 peritoneum below the arch of the transverse meso-colon ; this 

 is the terminal part of the first portion of the small intestine, 

 the duodenum. If the dissector will now hold the omentum 

 forwards he will be able to trace the duodenum from the 



