SMALL INTESTINE 



287 



inner and an outer layer of smooth or involuntary muscle fibres 

 which are separated by a thin connective tissue septum. The 

 inner circular layer is much thicker than the outer longitudinal. 



FIG. 236. FROM A LONGITUDINAL SECTION THROUGH THE WALL OF THE HUMAN SMALL 



INTESTINE. 



7, villi, and //, crypts of the mucosa ; ///, submucosa ; 1 V, circular, and F, longitu- 

 dinal layer of the muscular coat; I 7 /, serous coat; 0, i, and c, villi in transverse, oblique 

 and longitudinal section, respectively ; d, crypts in longitudinal, and , in transverse 

 section. Hematein and eosin. Photo, x 160. 



The regular disposition of the muscle fibres as an outer longi- 

 tudinal and an inner circular layer serves as a guide to the recog- 

 nition of the direction in which a given microscopical section has 

 been cut. In transections of the intestine the muscle fibres of the 

 outer layer of the muscular coat are transversely cut ; in longitu- 



