14t> II. DIGESTION AND ABSORPTION OF FATS 



absorbed in a fine emulsion. Although he recognized that as much as 12% 

 of the ingested fat could be split in the intestine, 696 he favored the concept 

 that the bulk of the fat was absorbed in the form of finely emulsified drop- 

 lets of neutral fat. This was the first definite statement of the current 

 particulate theory of fat absorption. The chief support for this concept 

 advanced by Munk was the fact that fat appears as neutral fat in the lym- 

 phatic system, 696 and hence is presumed to pass from the intestine through 

 the cells in fine droplets, 694 without chemical alteration. No good explana- 

 tion of the motivating force which brings this about was suggested. 



The method by which fat gains admission into the cells is one of the most 

 puzzling questions left unanswered by Schafer, Heidenhain and Munk. 

 One suggestion was that the striated outer border of the cells can form ame- 

 boid protrusions into the intestines whereby the cells are enabled to en- 

 gulf fat particles in the intestinal lumen and transfer them into the cell. 

 However, there is little histological evidence that these cells act as phago- 

 cytes, although Wotton and Zwemer 697 obtained photographs which appear 

 to show fat-like globules in the process of passing through the outer mem- 

 branes of the epithelial cells. However, Bloor 35 criticizes this conclusion 

 by stating that no proof is offered as to whether the droplets pictured rep- 

 resent unsplit fat or fatty acids. 



Another of the earlier theories to explain fat absorption is that of Pflii- 

 ger. 698 This investigator suggested that fats were hydrolyzed to fatty 

 acids and glycerol by lipase, that the fatty acids were neutralized by the 

 alkali present in bile and pancreatic juice, and that the sodium soaps so 

 formed and the glycerol, both of which are water-soluble, were easily trans- 

 ported across the mucosal wall. At some stage before the fat droplets 

 entered the lymphatics of the villi, a synthesis of glycerol and soaps to 

 neutral fat obtained. However, since the disclosure that the sodium soaps 

 are not stable at a pH below 8 and that the small intestine is practically 

 never alkaline, 641,642 the soap theory has lost much of its appeal. 



(6) Lipolytic Theory {Verzar). According to the Lipolytic Theory, 644 

 fats must be hydrolyzed to glycerol and fatty acids in the small intestine 

 before they can be absorbed. The greatest support for this hypothesis 

 has been brought forward in recent years by Verzar and his colleagues; 

 the work was summarized in the monograph of Verzar and MacDougall 554 

 and later by Verzar. 699 This theory has gained wide acceptance over much 



696 1. Munk, Arch. Physiol, 1879, 371-374. 

 \©R. M. Wotton and R. L. Zwemer, Anal. Record, 75, 493-503 (1939). 



698 E. Pfluger, Arch. ges. Physiol. (Pfluger's), 82, 303-380 (1900). 



699 F. Verzar, Arch. sci. physiol., 2, 43-63 (1948). 



