SECT. 147 ] MUSCULAR COATS OF ALIMENTARY CANAL. 317 



run obliquely upon the anterior and posterior wall of the stomach 

 towards the larger curvature, where they are partly attached by 

 elastic tendons (Treitz) to the outer surface of the mucous mem- 

 brane, and partly connected with each other (see the excellent 

 figures in Beau and Bonarmj, iii., PL 14). 



In the small intestines, the muscular coat is somewhat thicker 

 upon the duodenum and the upper parts than on the lower, 

 generally {'" to \'", and is composed only of longitudinal and 

 transverse fibres. The former are always thinner, and do not 

 form a complete layer, since they are very scanty, or even entirely 

 absent on the mesenteric border. They are usually most distinct 

 on the free border; still, even here, they are liable to be easily 

 stripped off with the peritoneum, so that the circular layer is 

 exposed. The latter is complete, enters into the folds of the ileo- 

 colic valve (valcula Bauhini) but not into the folds of Kerkring 

 (valvules conniventes), and consists of circular fasciculi, which not 

 unfrequently join together at acute angles. The musculus suspenso- 

 rius duodeni (Treitz) is a smooth muscle 1^ inch long, about 1 

 inch broad, and 1" thick, Avhich arises from the upper border of 

 the duodenum at the lower end of the latter, and passes, by means 

 of elastic tendons, into the dense connective tissue surrounding 

 the cceliac artery, and is also connected with slips coming from 

 the inner pillars of the diaphragm (I.e. tab. ii ). 



Upon the large intestine, the longitudinal fibres are reduced to 

 the three ligamenta coli. These are muscular bands, 4'" to 6"' or 

 even 8" broad, and \"' to \[" thick, which commence upon the 

 carina and coalesce upon the sigmoid flexure into two bundles 

 situated on the right and left, which, in conjunction with special 

 independent fibres, form the longitudinal muscular layer of the 

 rectum. Beneath these ligaments, there is situated a continuous 

 circular layer of fibres, which is thinner than upon the small 

 intestine, and particularly developed in the duplicatures, well 

 known under the name of plica sigmoidea. 



The rectum has a muscular layer upwards of \'" in thickness, 

 in which the longitudinal and at the same time thicker fibres are 

 situated externally, and the circular fibres internally. The lower, 

 somewhat thicker, termination of the circular muscular coat forms 

 the sphincter ani internus, with which the transversely striped 

 sphincter externus and levator ani are connected. The longitudinal 

 fibres terminate, according to Treitz, with elastic tendons which 

 are partly inserted into the pelvic fascia, partly penetrate the 

 sphincter ani externus, and are lost in the subcutaneous tissue of 



