Mucous coat 



I66o HUMAN ANATOMY. 



The muscular coat consists of a thicker layer of internal circular fibres and of 

 an external lon-itudinal one, the fibres of which are in most places collected into 

 three bands. Although longitudinal fibres exist between these they are few and 

 apparently not quite universal. Beginning in the caecum, at the base of the vermi- 

 form appendix, the three bands, or t*m* coli, continue along the large intestine as far 



as the sigmoid flexure, over which 



FIG. 1412. and the rectum the bands are 



only two, and no longer sharply 

 defined. In the rectum one is 

 on the front and the other the 

 stronger behind. The circular 

 fibres increase very much towards 

 the end of the rectum, the muscu- 

 lar apparatus of which will receive 

 special description (page 1675). 



The serous coat which once 

 surrounded the gut, in certain 

 places disappears during develop- 

 ment, and in others its arrange- 

 ment becomes modified by new 

 relations with other peritoneal 

 layers. These features will be 

 described with the parts con- 

 cerned. In structure it corre- 

 sponds with the serous coat of 

 other parts of the intestinal tube. 

 The appendices epiploicae 

 are little fringes or bags of perito- 

 neum containing fat hanging from 

 the large intestine. They may 

 be as much as 2.5 cm. (i in.) in 

 length, and are very prominent in 

 fat subjects, but in thin ones may 

 be overlooked. They are found 

 particularly on the inner aspects 

 of the ascending and descending 

 colon and on the lower one of 

 the transverse colon. It is often 

 stated that they occur along one 

 of the bands, but this relation is 

 at least not constant, although 

 they are generally arranged in a 

 single line. They are found also 

 on the sigmoid flexure. It is usu- 

 ally stated that they are not pres- 

 ent during childhood. Oddono, 1 

 however, has shown that they ap^ 

 pear in the fifth month of foetal life, first on the descending colon and sigmoid 

 flexure. We have seen them before birth. 



The blood-vessels, lymphatics, and nerves of the large gut in general 

 follow the arrangement already described in connection with the small intestine 

 1642). 



Serous coat 



Transverse section "f injritctl lar^e intestine, showing distribution 

 of arteries to coats. X 30. 



THE C^CUM. 



The oa'cutn, or blind gut, the first part of the large intestine, is a pouch hanging 

 at the junction of the ilmin and colon, from which the vermiform appendix 

 arises. The ilcum opens into the large intestine by a transverse orifice placed in- 



1 Dal Bollcttino dclla Societa Medico-Chirurgica di Pavia, 1889. 



