SOL UTION THEORIES OP FA T ABSORPTION. 45 5 



preparation of taurocholic acid in a pure condition from bile. He did not 

 pursue the subject further on its own account, and his statement is in part 

 erroneous, for the neutral fats scarcely dissolve at all in bile. In 1858, Marcet 1 

 published the results already described, showing the great solubility of the 

 fatty acids in bile when heated above their melting points. LatschinofF 2 

 described a variable compound, or rather mixture, formed by taurocholic acid 

 with a mixture of stearic and palmitic acids, which possesses certain crystallo- 

 graphic properties, but no definite chemical composition. 



Altmann, 3 mainly on histological grounds, concluded that fats are 

 not absorbed as an emulsion, but in some soluble form. 



Krehl, 4 under Altmann's direction, obtained sections of the intestine, 

 stained by osmic acid, from animals killed at varying times after feeding 

 on fat (olive oil and cream). These preparations showed a gradual 

 increase in the size of the globules with the advancement of the period 

 of digestion. Also, it was observed that in the earlier stages the 

 small fat globules showed a clear centre, surrounded by a dark ring. 

 From these appearances it was judged that the formation of the fat 

 granules was a gradual one from solution, and not from drops of fat 

 emulsion. In considering the soluble form in which the fats are 

 absorbed, Altmann rejects the idea that they are absorbed as soaps, 

 chiefly on the ground that the reaction in the small intestine of the dog 

 is acid, so that it cannot contain dissolved soaps ; 5 yet from such a por- 

 tion of intestine, with an acid reaction and containing a clear fluid, the 

 charged lacteals are often to be seen conveying away absorbed fat. 

 Altmann cites the statements as to the solubility of the fatty acids in 

 bile already mentioned, 6 and adds an experiment of his own, in which he 

 shows that a considerable, but not too great, quantity of a solution of com- 

 mercial glycerin soap, and then excess of hydrochloric acid, may be added 

 to a solution of sodium glycocholate or taurocholate without producing 

 any precipitation of either fatty or bile acid. From these data, and the 

 observation of Munk that the fatty material found in the dog's intestine 

 during fat digestion may contain as much as 12 per cent, of free fatty 

 acids, Altmann argues that the free fatty acids are dissolved in the 

 intestine by the bile acids. As the fatty acids so dissolved are absorbed, 

 fresh amounts of the neutral fats are decomposed, and the free fatty 

 acids so formed pass into solution to replace those removed by absorp- 

 tion. So that there is a cyclic process involving the decomposition of fats, 

 solution of fatty acids in the bile acids present, absorption of these fatty 

 acids by the intestinal cell, and regeneration of neutral fat within the 

 cell, accompanied by the appearance of fat granules. 



Altmann did not quantitatively determine the amount of solubility of 

 fatty acids in bile acids, bile, or intestinal fluid. The solubility in bile varies 

 greatly with temperature, as is shown by Marcet's experiments. 7 At the 

 temperature of the body the solubility is much less than at the temperature of 

 fusion of the fatty acids, but is still considerable ; while at ordinary atmo- 

 spheric temperature (14 to 15 C.) the solubility is very slight. 8 



The solubilities of the fatty acids, and mixtures of these at or near the 



1 See p. 444. 



- Ber. d. deutsch. chem. Gescllsch., Berlin, 1880, Bd. xiii. S. 1911. 



*Arch.f. Aiiat. u. PhysioL, Leipzig, 1889, Anat. Abth., Supp. Bd. S. 86. 



4 Ibid., 1890, Anat. Abth., S. 97. 



5 This objection is discussed under the soap-absorption theory. See p. 453. 



6 Except those of Marcet. 7 See p. 444. 



8 Moore and Rockwood, Journ. PhysioL, Cambridge and London, 1897, vol. xxi. p. 58. 



