290 PHYSIOLOGY OF ALIMENTATION. 



of the older observers that fat is absorbed chiefly in the form 

 of an emulsion was based upon physiological experiments 

 and histological studies which showed that in ordinary diges- 

 tion the fat of the food is emulsified in the lumen of the gut, 

 appears as droplets in the cells lining the gut, and in the same 

 form in the chyle, the fat-laden lymph which leaves the in- 

 testinal tract after a fatty meal. This conception was further 

 strengthened by the analytical results of physiological chem- 

 ists, who found but little fatty acid and alcohol (glycerine) in 

 any of these localities. The idea, therefore, that fat was ab- 

 sorbed in any other form than fat received little support, and 

 the formation of fatty acid and alcohol during digestion was 

 looked upon as of little importance. 



As the following will show, fat is in all probability absorbed 

 only after it has first been split into fatty acid and alcohol 

 and never in the form of the original foodstuff. The observa- 

 tions of RACHFORD and the recognition of the reversible 

 action of lipase suffice entirely to explain the facts cited 

 above which have so long been quoted in support of the older 

 ideas of fat absorption. 



Under normal circumstances fat is absorbed with great 

 rapidity from the intestinal lumen. From a physico-chemical 

 standpoint alone, therefore, it appears very unlikely that fat 

 enters the cells of the intestinal mucosa as such, for fat has 

 only slight powers of diffusion, especially into solvents made 

 up chiefly of water, such as protoplasm. To overcome this 

 argument the intestinal epithelium has been endowed with 

 powers of amoeboid motion and (hypo the tfcal) tubules sur- 

 rounded by contractile protoplasm. Even were its entrance 

 into the intestinal mucosa explained in this way, its exit into' 

 the lacteals and from here into the various tissues of the body 

 would yet have to be accounted for. The same explanation 

 could evidently not hold in all these cases of absorption. The 

 belief, on the other hand, that fat enters and leaves the intesti- 

 nal mucosa only in the form of its cleavage products in fact, 

 enters and leaves all tissues in this form meets with no such 



