E. SMALL INTESTINE. 

 BY E. VERSON. 



THE small intestine is a direct continuation of the stomach, 

 and, like this, consists of an external peritoneal investment 

 within which are two concentric tubes attached to one 

 another by more or less dense connective tissue. The outer of 

 these two is the muscular coat, the inner is the mucous mem- 

 brane. The -connective tissue forming the bond between them 

 presents various degrees of thickness, but no peculiarities of 

 structure:; iit contains a few elastic fibres and numerous con- 

 nective tissue corpuscles. 



The relative thickness of the two tubes to one another is too 

 variable to admit of any precise statement being given ; but 

 in a general way it may be said that the muscular tunic is 

 about three times as thick as the mucous, and that in Man the 

 thickness of the entire intestinal wall, including the peritoneum, 

 can scarcely be estimated at more than one millimeter. Measure- 

 ments, however, taken at various parts, will naturally exhibit 

 considerable variations according to the conditions of contraction 

 or relaxation present in the muscular fibres. 



The investing peritoneal coat is composed of ordinary con- 

 nective tissue with elastic fibres, and is either directly applied 

 to the muscular tunic, or is attached to it by means of a small 

 quantity of loose connective tissue. Its free surface is covered 

 by a single layer of pavement epithelium, the cells of which 

 seen in profile appear as thin scales with projecting nuclei. 



a. MUSCULAR COAT. 



The muscular tunic of the small intestine is differentiated 

 into two superimposed layers, which are distinguished in ac- 



