THE ALIMENTARY CANAL. 



83 



'); in the middle, it has a thickness 

 Fig. 200. 



the fundus it is thin (\— 

 of about J"'j in the 

 pyloric region, finally, 

 about % or even 1'". It 

 consists of three incom- 

 plete layers : 1. most 

 externally, longitudinal 

 fibres, especially at the 

 cardia, where they arise 

 from the expansion of a 

 part of the longitudinal 

 fibres of the oesophagus; 

 and also at the pylorus 

 and in the pars pylo- 

 rica, whence, tensely 



stretched, they are continued upon the duodenum ; 2. circular 

 muscles, in the middle region, from the fundus to the pylorus; 

 where they are accumulated, constituting the so-called sphincter 

 of the pylorus; 3. most internally, oblique fibres, which, in con- 

 nexion with the circular fibres, embrace the fundus as in a sling, 

 and run obliquely upon the anterior and posterior walls of the 

 stomach, towards its greater curvature, where they terminate upon 

 the outer surface of the mucous membrane or unite together. 



In the small intestine, the muscular coat is somewhat 

 thicker in the duodenum and the upper portions, than in the 

 lower ; it has, in general, a thickness of \ — J"' ', and is com- 

 posed only of longitudinal and transverse fibres, The former 

 are always less developed and do not form a continuous layer, 

 since they are very few or entirely absent along the attachment 

 of the mesentery; they are usually most distinct upon the free 

 border, though even here they may be readily torn away with the 

 serous membrane, so as, at once, to leave the second layer exposed. 

 The latter iscomplete aud continuous, consisting of circular bun- 

 dles, which not uncommonly anastomose at very acute angles. 



In the large intestine, the longitudinal fibres are reduced to the 

 three ligamenta coli, muscular bands of 4'" — 6"', or even 8'" 

 broad, and J — |"' thick, which commencing upon the caecum are 



Fig. 200. Stomach of Man, reduced: a, oesophagus, with the longitudinal fibres; 

 tr, transverse fibres (second layer), for the most part dissected off; tr, transverse 

 fibres of the fundus ; o.fibrce obliqna> ; p, pylorus ; d, duodenum. 



