THE BODY'S UTILIZATION OF FAT 427 



in the epithelial cells were made from absorbed fatty acid. Further, 

 the observation has been made that the fat particles in the epithelial 

 cells are small at the beginning of intestinal digestion, but that they 

 grow larger when the digestion has been in progress some time, as 

 though the droplets were made at the point where they are seen. Again 

 it has been shown that the fat ferment in the small intestine is 

 abundantly able to convert the fat of an ordinary meal completely into 

 fatty acid in the time usually required for a meal's digestion. 



However, it seemed difficult to understand how a drop of fat in con- 

 tact with an epithelial cell was first converted into fatty acid, then 

 absorbed by the cell and, before leaving the confines of the absorbing 

 cell, reconverted into a droplet of fat. But a similar transformation 

 is believed to occur in the case of proteid absorption. Proteids in 

 digestion are converted into peptone and thus absorbed, but no peptone 

 is found in the body, not even in the intestinal blood vessels, hence the 

 peptones must be at once reconverted into other proteids in the act of 

 absorption. 



The work of Kastle and Loewenhart makes it clear, in the case of 

 fat, how the reverse processes are brought about. Before referring to 

 their work let us remark that it is well known that the action of fer- 

 ments is never complete unless the product of the fermentation is re- 

 moved. To illustrate — if grape juice is fermenting to become wine, the 

 conversion of sugar to alcohol at first may be quite rapid, but by the 

 time a wine of ten per cent, alcohol is formed the alcohol present 

 inhibits the further action of the ferment. If the alcohol could be 

 removed from the wine, the action of the ferment would continue so 

 long as there was sugar present to ferment. 



Further, it has been shown that the action of a ferment may be 

 reversible, i. e., that the same ferment which will convert a solution of 

 carbohydrate A into carbohydrate B will also convert a solution of 

 carbohydrate B into a carbohydrate A. But, as just mentioned, the 

 action of no ferment is complete, hence whether we start with a solu- 

 tion of A or of B, the ferment action brings about a solution of A and 

 B in such proportion that ferment action ceases, i. e., the condition has 

 become one of chemical equilibrium. Kastle and Loewenhart worked 

 with the ferment lipase, whose known action was the conversion of 

 neutral fats into fatty acid and glycerine. They added the ferment 

 to a solution of fatty acid and were able to demonstrate the formation 

 therefrom of the neutral fat. 2 The importance of this observation is 

 very great. First, it adds another to the list of animal synthetic proc- 

 esses. Second, it offers an easily comprehended explanation of the 

 absorption of fat. For in case the small intestine contains neutral 

 fat immediately after a meal, the ferment will soon begi n to convert 

 2 They employed butyric acid and synthetized ethyl butyrate. 



