ABSORPTION OF FATTY PARTICLES. 399 



With regard to the forces concerned in the absorption of fats, 

 v. Wistinghausen proved, that when a porous membrane is moistened 

 with bile, the passage of fatty particles through it is thereby facilitated, 

 but this fact alone does not explain the copious and rapid absorption 

 of fats. It appears probable, that the protoplasm of the epithelial cells 

 is actively concerned in the process, and that it takes the particles into 

 its interior. Perhaps a fine protoplasmic process is thrown out by 

 these cells, just as pseudopodia are thrown out and retracted by lower 

 organisms. It is possible that absorption may take place through the 

 open mouths of the goblet-cells. The protoplasm of the epithelial cells 

 is in direct communication with the numerous protoplasmic lymph-cells 

 within the reticulum of the villi, so that the particles may pass into 

 these, and from them through the stomata (?) between the endothelial 

 cells into the central lacteal of the villus. According to this view, the 

 absorption of fatty particles, and perhaps also the absorption of true 

 proteids, is due to an active vital process, as indicated by the observa- 

 tions of Briicke and v. Thanhoffer. This view is supported by the 

 observation of Griinhagen, that the absorption of fatty particles in the 

 frog is most active at the temperature at which the motor phenomena 

 of protoplasm are most lively. That it is due to simple filtration alone 

 is not a satisfactory explanation, for the amount of fatty particles in the 

 chyle is independent of the amount of water in it. If absorption was 

 chiefly due to filtration, we would expect that there would most 

 probably be a direct relation between the amount of water and the fat 

 (Ludwig and Zawilsky). [The observations of Watney have led him 

 to suppose that the fatty particles do not pass through the cell 

 protoplasm to reach the lacteal, but that they pass through the cement- 

 substance between the epithelial cells covering a villus. If this view 

 be correct, the absorbing surface is thereby greatly diminished.] 



[Schafer suggests that the leucocytes, which have been observed 

 between the columnar cells of the villi of the small intestine, are carriers 

 of at least part of the fat from the lumen of the gut to the lacteal ; they 

 also, perhaps, alter it for further use in the economy (p. 389)]. 



The activity of the cells of the intestine with pseudopodial processes may be 

 studied in the intestinal canal of Distomum hepaticum. Sommer has figured these 

 pseudopodial processes actively engaged in the absorption of particles from the 

 intestine. 



Spina observed that the intestinal epithelium of the larvse of flies shortened 

 when they were stimulated with electricity, and absorbed fluid from the intestinal 

 canal. The cells of the villi of the frog also react to electrical stimulation. 



The increase in the size of the cells occurs simultaneously with the contraction 

 of the intestine. Spina also supports the view that the cells, in virtue of their 

 activity, possess the property of absorbing fluid from the intestinal contents and 

 again giving it up. An exchange of fluids in the opposite direction never takes place. 



The statements of former observers that particles of charcoal, pigments, and 



