On the Functions of the Bile as a Solvent. 



65- 



By others the bile has been regarded as an anti-putrefactive, although 

 it readily undergoes putrefaction itself. Others, without much experi- 

 mental proof, have suggested that it stimulates the intestinal epithe- 

 lium and increases peristalsis, but even if this be allowed it leaves 

 much of the action of the bile untouched. While it is universally 

 admitted that bile exhibits at most only unimportant traces of a diges- 

 tive action on food-stuffs, some observers state that its presence favours 

 and increases the activity of other digestive fluids upon carbohydrates, 

 fats, or proteids, and see in this an important function of the bile.* 

 On the other hand, it is stated by other experimenters that this aiding 

 power of the added bile is no more than can be explained by the altera- 

 tion in chemical reaction of the mixed fluid. f 



With regard to the action of bile in favouring fat absorption, one 

 view which has been held is that the bile alters the physical character 

 of the intestinal epithelium when it wets it, and in some physical way 

 makes the conditions more favourable for the taking up of emulsified 

 fats. Since it is very probable, however, that all the fat is absorbed 

 in some soluble form, and not as an emulsion, this theory of biliary 

 activity falls to the ground. 



It was first suggested by Altmann,J mainly from histological obser- 

 vations, that bile aided fat absorption by dissolving the fatty acids set 

 free from the neutral fats in the intestine. Marcet§ had shown before 

 this that bile dissolves free fatty acids to a clear solution, and later 

 Moore and EockwoodjJ determined the solubilities of fatty acids in bile,, 

 and further demonstrated that in some classes of animals a certain 

 amount of the fat was absorbed as dissolved free fatty acid. 



The latter authors, while admitting that a considerable amount of 

 absorption of fat as dissolved free fatty acid occurs in carnivora, and 

 insisting upon the importance of bile as a solvent in this connection, 

 showed from a consideration of the reaction of the intestinal contents 

 during active fat absorption that in other species of animals practically 

 all the fat was absorbed as dissolved soaps. Even in carnivora it was 

 further shown that in addition to the absorption as free fatty acid dis- 

 solved by the bile, a considerable amount of absorption as dissolved 

 soaps takes place. 



The soaps formed in the intestine during the digestion of fat are 

 chiefly sodium soaps. Now it has universally been taken for granted 

 that these are easily soluble in water, and no one has considered any 

 action of the bile as necessary to their solution in the intestinal con- 



* Rachford, ' Journ. of Physiology,' 1899, vol. 25, p. 165. 



f Chittenden and Albro, ' Amer. Journ. of Physiol.,' 1898, vol. 1, p. 307. 



X 1 Arch. f. Anat. u. Physiol.,' 1889, Anat. Abth. Supp. Bd., p. 86. 



§ ' Eoy. Soc. Proc. Lond.,' toI. 9, 1868, p. 306. 



|| 'Roy. Soc. Proc.,' vol. 60, 1897, p. 438; 'Journ. of Physiol.,' vol. 21, 1897, 

 p. 58. (In this paper the literature of the subject is given.) 



