DIGESTIVE ORGANS LARGE INTESTINE. 



535 



be seen hereafter, there is reason to believe, that digestion of the ali- 

 ment, which has escaped change higher up, occurs. 



The colon is by much the longest of the large intestines, (Fig. 

 210.) It is a continuation of the caecum, from which it cannot 

 be distinguished; but is con- 

 sidered to commence at the Fi - 243 - 

 termination of the ileum. 

 From the right iliac fossa it 

 ascends along the right lum- 

 bar region, over the kidney, 

 to which it is connected. It 

 is, in this part, called colon 

 dextrum, ascending or right 

 lumbar colon. From the kid- 



nev it DaSSeS forwards and Muscular Coat of the Colon, as seen after the removal 

 J , , of the Peritoneum. 



crosses the abdomen in the 



. . , , . 1,1. One of its three bands of longitudinal muscular 



epigastric and hypochondriac fibres. 2, 2. Circular fibres of the muscular coat. 



regions, being connected to 



the duodenum. This portion is called great arch of the colon, colon 

 transversum. The right portion of the great arch is situate under the 

 liver and gall-bladder ; and hence is found tinged yellow after death, 

 owing to the transudation of bile. The left portion of the arch is situate 

 under the stomach ; and, immediately below it, are the convolutions of 

 the jejunum. In the left hypochondre, the colon turns backward under 

 the spleen, and descends along the left lumbar region, anterior to the 

 kidney, to which it is closely connected. This portion is termed colon 

 sinistrum, descending or left lumbar 

 colon. In the left iliac region, it forms 

 two convolutions, which have been com- 

 pared to the Greek $, or to the Roman 

 s; and hence this part of the intestine 

 has been designated sigmoid flexure, 

 Roman s, or iliac turn of the colon. 

 This flexure varies greatly in length 

 in different persons, extending fre- 

 quently into the hypogastric region, 

 and, in some instances, as far as the 

 caecum. The colon, through its whole 

 extent, is fixed to the body by the 

 mesocolon. 



The coats of the great intestine are 

 the same in number and structure as 

 those of the small; but are thinner, 

 and not as easily separable by dissec- Longitudinal Section of the End of the 



mi J " . J . , lleum, and of the Beginning of the .Large 



tion. Ihe mucous membrane is less 

 villous and velvety. The most cha- 

 racteristic difference, however, in their , muscuiar cuai , COVB1CU uy ^ . , 



general appearance, is the pouched 5 - Areoiar and mucous coats, e, 6 Folds of 



r 4_ mucous coat at this end of the colon. /, 7. 



Or Cellular aspect Of the former. Prolongations of areolarcoaHnto these folds. 



These pouches are reservoirs for excre- 



Intestine. 



1,1. Portion of the ascending colon. 2, 2. 



Union of the 



