PHYSIOLOGICAL ABSORPTION. 347 



conversion was here originally considered to be brought 

 about by the cells of the Peyers patches (Brown and 

 Heron), but more recent work by Miss Tebb seems to show 

 that the mucous membrane of the intestine is far more 

 active in the process, though it must be admitted that many 

 tissues effect the change. 



The interesting syntheses of neutral fats from fatty 

 acids will be referred to below. 



It is not my intention in this article to follow the absorp- 

 tion of solutions any further, but it must be stated that the 

 fact that such solutions reach the organism by the blood 

 stream instead of the lacteals is, as Heidenhain has pointed 

 out, easily accounted for by the fact that the capillaries of 

 the villus lie in contact with the absorbing cells. If, how- 

 ever, a great excess of solution is present in the gut, as 

 Ginsberg has pointed out for sugar, and Wertheimer for 

 solutions of indigo carmine, a diffusion within the villus 

 parenchyma may go on into the lacteal, so that the sub- 

 stances appear in the chyle. 



If we now consider briefly the question of the absorption 

 of fats, it will be evident that in spite of numerous researches, 

 the actual process is far from being understood. 



With regard to the question whether the fat passes 

 through the bodies of the columnar epithelial cells, in the 

 cement between them (Watney), or is transported by 

 wandering cells (Schaefer and Zawarykin), the majority of 

 observers maintain that the first-mentioned channel is the 

 one normally used. Fat certainly appears betw r een the 

 columnar cells in microscopic preparations at times, but it is 

 probably forced there from the villus parenchyma, during 

 the contraction of the villus muscle that occurs when the 

 tissue is plunged into the fixative, for fat is not so found 

 between the cells of the non-muscular processes of the frog's 

 gut (Heidenhain). Fat granules in leucocytes also un- 

 doubtedly occur, but Zawarykin s idea of the great preval- 

 ence of fatty leucocytes during digestion is, according to 

 Heidenhain, an error of observation due to mistaking the 

 granules of the oxyphil leucocytes for fat on account of their 

 black reaction with osmic acid. 



