1903.] Fats accompanying Absorption from the Intestine. 135 



It is true that the change is currently believed to take place in the 

 columnar cells of the intestine, but a review of the experimental 

 evidence on which this statement rests will suffice to show that the 

 proof is incomplete, and hence the subject has here been more rigorously 

 investigated. 



The chief facts for the view that the synthesis occurs in the intestine 

 are, the histological appearance presented by the columnar cells when 

 taken during fat absorption and examined by the usual micro-chemical 

 tests for fats ; secondly, the naked-eye appearance of the mesenteric 

 lacteals and microscopic examination of their contents during fat 

 absorption ; and, thirdly, the supposed action of extracts of intestinal 

 mucous membrane in synthesizing, in vitro, neutral fats from solutions 

 of soap and glycerine. 



The objections to these supposed proofs are, that the histological 

 and naked-eye appearances taken to be characteristic of fat in the 

 columnar cells and mesenteric lacteals might equally well be given by 

 free fatty acid in suspension, and hence supply no proof of a synthesis 

 of neutral fat, since no chemical examination of the fatty matters 

 present at these stages in fat absorption have hitherto been made so 

 far as the author is aware. In the second place, the proofs given of 

 the synthesis of neutral fat in vitro from soap and glycerine by intestinal 

 cells are based upon incomplete analyses, and, as will be shown later, 

 are erroneous. 



It may be stated at once, however, that the present investigation has 

 shown that the synthesis does occur in the intestinal mucosa, or, to 

 put the matter more rigorously, before the mesenteric lacteals have 

 been reached, but that it has been impossible to imitate this action in 

 vitro either by detached cells or cell-free extracts. 



There are two places along the path of the absorbed fatty material 

 from intestine to thoracic duct at which the lymph comes into intimate 

 relationship with cells, and at which accordingly chemical changes might 

 be expected to occur. These situations are the intestinal villus and the 

 mesenteric lymphatic gland, and the experimental method of procedure 

 suggests itself of examining the chemical composition of the fatty 

 matter in these situations, and before and after passing through them. 

 This method has been employed in the present investigation, and in so 

 doing the percentage of neutral fat and of free fatty acids have both 

 been directly determined in ethereal extracts of the intestinal 

 mucosa, and lymph of the mesenteric lymphatic vessels obtained 

 during fat absorption. 



The lymph in the mesenteric lacteals during fat absorption has not 

 previously been examined chemically as to its content in neutral 

 fat and free fatty acid, probably from the difficulty experienced in 

 collecting it in sufficient quantity from the exceedingly narrow 

 vessels. 



