214 HERBERT WATNEY. 



views which various observers have held about the small 

 cells among the epithelium. 



The methods which were employed are then given ; 

 chromic acid and chloride of gold were used as hardening, 

 reagents ; osmic acid as a means of distinguishing the position 

 of the fat particles. 



The structure of the epithelium and the nature of the 

 tissues found among the epithelial cells are next described. ' 



It was foundj in contradistinction to the research of Than- 

 hoffer, that the epithelial cells are closed, and it is also shown 

 that they have no processes stretching into the mucosa. 

 Attention is drawn to the fact that most authors who have 

 asserted that the epithelial cells have processes have worked 

 too exclusively with the intestine of the frog, and seem to have 

 been unaware of the extreme length of the epithelium in that 

 animal, and of the different lengths of the epithelium in 

 different parts of the intestine, and even in a single villus 

 (see PI. XV, fig. 1). 



It was found that among the epithelial cells small round 

 cells are seen similar to the lymph-corpuscles of a lymphatic 

 follicle (see 1. c, fig. 1), and in addition to these cells groups 

 of young epithelial cells, which are called " epithelial buds" 

 (see fig. 6). It is also shown that a reticulum, similar to 

 and continuous with that which exists in the lymphoid fol- 

 licles and in the villi, can be traced everywhere among the 

 epithelium of the intestine, the reticulum appearing in ver- 

 tical sections of the epithelium as fine, almost thread-like, 

 processes, continuous with the dark line on which the epi- 

 thelium appears to rest. This dark line (see fig. 1, r) is due 

 to the sectional viewof the connective-tissue reticulum which 

 lies surrounding the epithelial cells. In transverse sections 

 of the epithelium the reticulum appears as star-shaped bodies 

 united by processes. 



As regards the membrana propria of the villi, appearances 

 are found somewhat similar to those figured in the long-lost 

 sight of research of Eberth, that is to say, there is a definite 

 membrane (not, as the older authors held, a greater condensa- 

 tion of retiform tissue), the membrane being formed chiefly 

 of cells, as was pointed out by Debove ; and it is also shown 

 that the endothelial cells of which it is composed are very 

 similar to the cells forming the upper part of the villus (see 

 e, fig. 1). It is also demonstrated that a reticulum con- 

 tinuous with that of the villus, holds in its meshes the 

 endothelial-like cells of the membrane. 



The tissue of the villus is composed, not, as has been so 

 often described, of branched connective-tissue corpuscles or 



