i66o 



HUMAN ANATOMY. 



Fig. 



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

 an external longitudinal 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 tania coli, continue along the large intestine as far 



as the sigmoid flexure, over which 

 ^412. aj^(j thg 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 



Mucous coat 



Submucous 

 coat 



Circular 

 muscle 



rtT'"^*" , .... 



y5| Longitudmal 



''^- ' muscle 



Serous coat 



Transverse section of injected large intestine, showing distribution 

 of arteries to coats. X 30. 



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,^ 

 however, has shown that they ap- 

 pear in the fifth month of fcetal 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 ari'angement already described in connection with the small intestine 

 (page 1642). 



THE C^CUM. 



The caecum, or blind gut, the first part of the large intestine, is a pouch hanging 

 downward at the junction of the ileum and colon, from which the vermiform appendix 

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



' Dal Bollettino della Societa Medico-Chirurgica di Pavia, 1889. 



