146 THE AMERICAN MONTHLY [May, 



the muscular and the mucous coats. The sub-mucous 

 coat is the seat of the supply vessels and nerves in all 

 parts of the alimentary canal, in the section of the small 

 intestine, p. 149, is shown how the artery bores its way 

 straight through the muscular coat, not at that time giv- 

 ing oflF any branches, but reserving them to be given off 

 in both directions from trunks which lie in the sub- 

 mucous coat. The mucous coat is composed of tubular 

 glands which are generally branched near the surface 

 into three or four simple straight tubes running verti- 

 cally to the surface of the coat. These tubes are so 

 closely packed that at first it is very difficult to analyze 

 the appearance of the section and to distinguish that in 

 the confusion of cells there is any definite structural 

 order. In an injected specimen the capillary arrange- 

 ments are clearly displayed, but the grandular structure 

 is equally difficult to recognize. The vertical section 

 (see frontispiece) shows, somewhat diagrammatically, 

 the actual mode of arrangement of the different parts 

 of the mucous coat. 



At '' a " and "b " are the openings into the stomach of 

 the ducts of the glands, in the depth of each of these 

 there is a row of cells running down close beside others 

 of the same sort, these, as seen in the one opening at "a" 

 are in the form of a long and narrow tube with a central 

 lumen, two tubes are shown here opening by a single duct. 

 The high power shows the character of the cells in the 

 wails of these tubes, these cells are different at different 

 levels, at the summit they are tall and very slender with 

 a long and narrow nucleus, the "outer ends of the cells 

 are rounded showing their soft character as in the free 

 portions of cells in the liver. The cells on the free sur- 

 face of the duct are vertical to the surface, and in the 

 deeper parts of the duct they are again vertical, but be- 

 tween these points they are oblique, leaning upward, the 

 cells are nearly transparent containing very little stain- 



