Greene. — Absorption of Fats in Salmon 263 



fat in the epithelium varied greatly in amount. The varia- 

 tion was so great that the question was immediately raised 

 as to the source and nature of this fat. 



Two hypotheses are possible in explanation, first, that 

 the fat droplets were present merely as storage fat. If so 

 it could legitimately be expected that the fat should have 

 an even distribution through the various portions of the 

 epithelial coat of the ccecum, also that there would lie some 

 uniformity of distribution in the different coeca of one and 

 the same fish even though there might be variations in 

 different fishes. The facts did not correspond with this 

 expectation, as the previous statements have already in- 

 dicated. 



The second hypothesis in explanation of the facts ob- 

 served is that the epithelial fat was in process of absorption. 

 This hypothesis was supported, first, by the fact that the 

 salmon under observation were feeding salmon, the food 

 consisting of the Crustacea, molluscs, and other fishes of the 

 region, many having a high percentage of fat in their com- 

 position. Furthermore, if the epithelial fat were absorption 

 fat it certainly would vary in amount in different portions 

 of the coat. Those portions of the epithelium in which ad- 

 jacent folds are in contact would receive a relatively small 

 amount of fat for absorption. Those portions of the mu- 

 cous coat extending in folds well out into the middle of the 

 lumen of the ccecum would naturally have a better contact 

 with the food than the deeper portions just mentioned and 

 have access to more fat. 



The relation of the mucous epithelium to the other por- 

 tions of the ccecal structure can be seen in the sections show- 

 ing fat absorption. Highly magnified portions of the epithe- 

 lium show the cells charged with fat. In some preparations 

 the free ends of the epithelial cells are filled with relatively 

 large sized fat droplets in that portion of the cell nearest 

 the nucleus. In the extreme distal ends of the cells of these 

 sections the fat is in very minute droplets, discernible only 

 with the oil immersion lens. The material also shows a 



