A BSORPTION OF FA TS. 461 



studied. It was found that food passed very rapidly through the alimentary 

 canal without much modification, scarcely any fat was absorbed, but it was 

 nearly all converted into fatty acid. 



These varied results may be summed up as showing that both the 

 pancreatic juice and the bile are powerful aids in the digestion and 

 absorption of fats, but neither is absolutely indispensable. 



The view to be taken of the part played by bile and pancreatic juice 

 in fat absorption must naturally vary with the view held as to the form 

 in which fat is absorbed. 



1. It may be urged that, in the absence of pancreatic juice, a sufficient 

 supply of fatty acid is not set free for emulsification of the remainder. 

 Since bile (or bile salts) very much hastens the fat-splitting action of 

 pancreatic juice, 1 the absence of bile would have a very similar effect to 

 that of pancreatic juice itself. A serious objection to this explanation 

 lies in the fact that in defective absorption, due to the absence of either 

 bile or pancreatic juice, nearly all the unabsorbed fat is found in the 

 faeces as free fatty acid. 



It might be claimed that this fat-splitting, probably by bacterial 

 action, takes place much lower down in the intestine, at a less favourable 

 position for absorption, and that a considerable part of the intestine is 

 traversed before a sufficient amount of fatty acid is formed. But in the 

 faeces as much as 80 per cent, of the total fat is as free fatty acid, while 

 only about 5 per cent, is required for spontaneous emulsion ; besides, the 

 fat of the food contains nearly sufficient fatty acid to begin with, so that 

 this contention has little weight. 



2. Another view which has been held is, that in the absence of either 

 bile or pancreatic juice the intestinal reaction is acid, so that no emul- 

 sion can take place, and hence the fat cannot be absorbed. It is not, 

 however, claimed that such an acid reaction is due to free hydrochloric 

 acid, since the remaining alkaline secretions are still more than sufficient 

 to neutralise this, and active fat absorption has often been observed in 

 presence of an acid reaction due to organic acids. 



3. It has been supposed that the absence of the proteid of the 

 pancreatic juice has an unfavourable effect on the formation of an 

 emulsion (Minkowski). 



4. A theory advanced by v. Wistinghausen 2 was that the bile aided 

 fat absorption by mechanically wetting the epithelial cells with a fluid 

 which rendered the passage of the fat easier. He claimed that oil 

 stood higher in capillary tubes wetted with bile than in similar tubes 

 wetted with water, and that oils or melted fats passed more rapidly 

 through a membrane wetted with bile than through one wetted 

 with water. These results have not, however, been confirmed by other 

 observers. 3 



5. It has also been supposed that the bile directly stimulates 

 (chemically) the epithelial cells of the intestine to increased fat absorp- 

 tion, and that in the absence of the bile this stimulus is absent. Under 

 these conditions the epithelial cells either do not absorb fat as an emul- 



1 Rachford, Journ. Physiol., Cambridge and London, 1891, vol. xii. p. 87. 



2 Translation in Arch. f. Anat. u. Physiol. , Leipzig, 1873, S. 137, by J. Steiner. See 

 also Schiff, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1857, Bd. ii. S. 345; Heiden- 

 hain, Arch. f. d. ges. Physiol.. Bonn, 1888, Bd. xliii. Supp. Heft, S. 91. 



s Groper, Arch. f. Anat. u. Physiol., Leipzig, 1889, S. 505. 



