296 DIGESTION 



conception. Free fatty acids are very well absorbed from the intestine even 

 when their melting point is higher than 50 C. and when they cannot there- 

 fore become fluid in the body (I. Munk). The fine emulsion., known by the 

 name of chyle, is in many cases entirely wanting from the intestine of 

 the dog; and even when chyle is introduced into the intestine, the fine emul- 

 sion entirely disappears after three hours, and there is found now only larger 

 fat drops surrounded by a turbid granular mass. Lanolin which is a mixture 

 melting at 40 42 C., made up of compounds of fatty acids with cholesterin, 

 isocholesterin, etc., very difficult to split into their constituents, is not ab- 

 sorbed at all from the intestine of the dog (Cohnstein). Finally the histolog- 

 ical findings in preparations of the intestinal mucosa made during absorption 

 of fat are of such a character that they can scarcely be explained from the 

 standpoint of the emulsion hypothesis (cf. page 304). 



Against the emulsion hypothesis it has been observed also that in the dog 

 the reaction throughout the greater part of the small intestine is acid in spite 

 of very active absorption of fat ; and in man the reaction of the small intestine 

 is said to be acid. This reaction, however, is caused by an excess of org-anic 

 acids and of carbon dioxide, and cannot be adduced as proof against an eventual 

 formation of soaps (Moore and Rockwood). 



In the light of these facts the emulsion theory cannot be looked upon as 

 sufficiently well founded, and in fact another possibility is at hand to explain 

 the absorption of fats. This is, that the fats are completely decomposed in the 

 intestine and that the fatty acids formed are absorbed either as soaps or in a 

 solution brought about by the bile. 



This view, advocated especially by Altmann, Pfliiger, Moore and Eatch- 

 ford, and supported by many histological facts, is not contradicted by anything 

 known concerning the extent of the decomposition of fats in the intestine, 

 for that decomposition is in fact very great. To find, after feeding neutral 

 fat, that some of it is not decomposed, of course proves nothing against the 

 assumption, for the free fatty acids are absorbed as they are formed, and if 

 the absorption goes on properly they might never be present in large quantity 

 in the intestine. 



It has been known since Strecker's time (1848) that bile and bile salts dis- 

 solve fatty acids quite easily. One hundred c.c. of dog's bile can dissolve 6 g. 

 of mixed fatty acids from swine's fat, 5.5 g. from ox fat and 2 g. from sheep's 

 fat. The solubility of the fatty acids in the bile depends therefore essentially 

 on the presence of oleic acid, which has been shown also by direct experiment. 

 The bile salts of themselves have a much smaller solvent power than the bile, 

 among whose constituents lecithin must be the most important for this action. 

 The solubility of soaps is increased also by the bile. 



After exclusion of bile from the intestine, the absorption of fats declines 

 considerably a fact very easily understood in the light of the conception now 

 under discussion. But even under these circumstances a certain quantity is 

 absorbed, probably in the form of soaps. In the intestinal contents there is 

 always found under normal circumstances more alkali than is necessary for the 

 neutralization of the inorganic acids present, and there occurs as a consequence 

 a certain amount of saponification. The soaps as they are taken up by the 



