FAT-ABSORBING FUNCTION OF ALIMENTARY TRACT OF KING SALMON. 169 



they vary in size. The cells have all the appearance of cells in sections cut through 

 the pyloric coeca of this fish where large quantities of fat are known to have been present, 

 but is of course now dissolved out by the oils used in imbedding the material in paraffin. 

 In the cells of the superficial epithelium of the stomach the clear areas are smaller and 

 do not form so large a proportion of the body of the cell as in the epithelium of the 

 pyloric cceca. 



Also, through the superficial epithelium one finds black round globules of rela- 

 tively small size in the middle of the body of the cell. These black dots correspond 

 to the areas above the nucleus which scarlet red shows to contain fat. (Fig. 4.) In 

 the base of the cells, especially in the cells of the outer folds of the epithelium, the same 

 black granules are present. Undoubtedly all these black granules are due to fat stained 

 with osmic acid. The neck cells of the crypts do not contain the black granules in the 

 main body. The black staining in salmon no. 45 is limited to the ends of the cells. 



ABSORPTION IN THE PYLORIC STOMACH. 



The difference in structure of the pyloric stomach mucosa has already been described 

 in a previous paper presenting the normal structure of the alimentary tract. " This divi- 

 sion of the stomach is a much more active region for fat absorption than is the cardiac 

 division. The main portion of the pyloric division shows more numerous fat droplets 

 in the cylindrical cells than is shown by the cardiac epithelium in an experimentally 

 fed animal. 



In the region near the pyloric valve the fat fills the more superficial epithelial cells to 

 a maximum. The amount more nearly approaches that in the intestinal mucosa, although 

 the fat droplets never reach the relatively large size of those of the cells of the latter 

 region. A reference to figures i , plate xii, and 4, plate xiii, will reveal the comparative 

 amounts of fat in different gastric epithelial regions. The crypts of this portion of the 

 pyloric stomach are more open and the fat is more often found in the lining cells of 

 their walls, even down to the bottoms of the crypts. Yet, in the most heavily fat- 

 loaded preparations there are always some crypts that show no fat while others may 

 be quite red with the stained droplets. 



In the pyloric stomach, where the epithelial cells are morphologically intermediate 

 in character between the gastric type and that of the intestine, one can not but make 

 the inference that the absorptive power is also intennediate in degree. Yet the epi- 

 thelial cells of the free surface of the mucous fold are distinctly gastric in character, as 

 has already been described. The cells of the free surfaces are most loaded with fat, 

 as figure i, plate xii, shows. Another point of comparison is found in the fact that the 

 fat droplets in the epithelium of the extreme caudal end of the pj-loric stomach are 

 very much smaller in size than the droplets of the cells of the intestinal epithelium 

 just on the other or intestinal side of the pyloric valve. Sections of the pyloric stomach 

 have been prepared in which the first whorl of coeca lying close around the wall of this 

 part of the stomach were also cut. The epithelial coats of the coeca were in every 

 instance filled with very large fat droplets. The fat droplets were four or five times 

 larger in diameter than the droplets in the neighboring pyloric gastric epithelium. 



« Greene, op. cit. 



