CAECUM. COLON. 567 



commencement of the large intestine. It is situated in the right iliac 

 fossa, and is retained in its place by the peritoneum, which passes 

 over its anterior surface; its posterior surface is connected by loose 

 areolar tissue with the iliac fascia. Attached to its extremity is the 

 appendix vermiformis, a long worm- shaped tube, the rudiment of the 

 lengthened caecum found in all mammiferous animals except man and 

 the higher quadrumana. The appendix varies in length, from one to 

 five or six inches ; it is about equal in diameter to a goose-quill, and is 

 connected with the posterior and left aspect of the caecum near the 

 extremity of the ileum. It is usually more or less coiled upon itself, 

 and retained in that coil by a falciform duplicature of peritoneum. 

 Its canal is extremely small, and the orifice by which it opens into 

 the caecum not unfrequently provided with an incomplete valve. 

 Occasionally the peritoneum invests the caecum so completely as to 

 constitute a meso-caecum, which permits of an unusual degree of 

 movement in this portion of the intestine, and serves to explain the 

 occurrence of hernia of the caecum upon the right side. The cascum is 

 the most dilated portion of the large intestine. 



The Colon is divided into ascending, transverse, and descending. 

 The ascending colon passes upwards from the right iliac fossa, through 

 the right lumbar region, to the under surface of the liver. It then 

 bends inwards, and crosses the upper part of the umbilical region 

 under the name of transverse colon, and on the left side descends 

 (descending colon) through the left lumbar region to the left iliac 

 fossa, where it makes a remarkable curve upon itself, which is called 

 the sigmoid flexure. 



The ascending colon, the most dilated portion of the large intestine, 

 next to the caecum, is retained in its position in the abdomen either 

 by the peritoneum passing simply in front of it or by a narrow meso- 

 colon. It is in relation in front with the small intestine and abdomi- 

 nal parietes ; behind with the quadratus lumborum muscle and right 

 kidney ; internally with the small intestine and the perpendicular por- 

 tion of the duodenum ; and by its upper extremity with the under sur- 

 face of the liver and gall-bladder. The transverse colon, the longest 

 portion of the large intestine, forms a curve across the cavity of the 

 abdomen, the convexity of which looks forwards and sometimes down- 

 wards. It is in relation by its upper surface with the liver, gall- 

 bladder, stomach, and lower extremity of the spleen ; by its lower sur- 

 face with the small intestine ; by its anterior surface with the anterior 

 layers of the great omentum and the abdominal parietes ; and by its 

 posterior surface with the transverse meso-colon. The descending colon 

 is smaller in calibre, and is situated more deeply than the ascending 

 colon. Its relations are precisely similar. The sigmoid flexure is the 

 narrowest part of the colon ; it curves in the first place upwards and 

 then downwards, and to one or the other side, and is retained in its 

 place by a meso-colon. It is in relation in front with the small intes- 

 tine and abdominal parietes ; behind with the iliac fossa, and on either 

 side with the small intestine. 



