SOL UTION THEORIES OF FA T ABSORPTION. 45 1 



converted into fats somewhere on their way from the intestine to the 

 thoracic duct. He is hence of the opinion that in the normal course of 

 digestion a considerable but indeterminate amount of fat may be 

 absorbed in the form of emulsified fatty acids. 



Munk's experimental results as to the absorption and synthesis 

 during the process of absorption of the fatty acids, are of the highest 

 importance ; but it in no wise follows from them that the fatty acids 

 are absorbed in the form of an emulsion. Such a theory is subject to 

 the same objections as have above been urged against the older theory 

 of absorption as emulsified fats. The fatty acids are probably taken 

 up from the intestine by the epithelial cells in some soluble form, and 

 synthesised to neutral fats in these cells. 



Solution theories of fat absorption. Theory of absorption as 

 soaps. One of the most important theories of fat absorption in soluble 

 form is, that the neutral fats are split up by the action of the pancreatic 

 enzyme into fatty acids and glycerin, that the fatty acids unite with a 

 part of the alkali of the intestinal secretions to form alkaline soaps 

 which are soluble in water, and that the alkaline soaps and glycerin 

 are absorbed in solution by the epithelial cells, and there synthesised 

 back to neutral fats. This theory is supported by a good deal of 

 experimental evidence. Eadziejewski 1 showed that alkaline soaps were 

 absorbed ; Perewoznikoff, 2 that a mixture of alkaline soap and glycerin 

 was absorbed and synthesised to neutral fat. The lacteals had the usual 

 milky appearance seen after a fatty meal; microscopic preparations, 

 stained with osmic acid and with alkanna, showed in the tissue of the 

 villi, and in the epithelial cells, fat globules of varying size. Will, 3 work- 

 ing under Griinhagen's direction, confirmed these results by histological 

 observations on the frog; further, he showed that the presence of 

 glycerin was unnecessary. Will made two kinds of experiments. In 

 one he fed the frogs, which had previously been deprived of food, 

 with the materials to be tested ; in the other, he injected the materials 

 into the living but cut out intestine, and then examined teased speci- 

 mens stained with osmic acid. In both series the same results were 

 obtained, on feeding with a mixture of pure palmitic acid and glycerin, 

 or of potassium palmitate and glycerin; at the end of twenty-four 

 hours an examination of the villi showed a formation of fat, by the 

 presence everywhere of large distinct fat globules. Injection of palmitic 

 acid alone into the intestine also led to the appearance of fat globules 

 in the epithelium, 4 but these were not nearly so numerous as in the 

 cases in which the palmitic acid was mixed with glycerin. As 

 Salkowski and Munk had shown that fatty acids can be emulsified 

 under certain conditions, 5 Will proceeds to show that this could not be 

 the case in his experiments, and that the fat globules blackening with 

 osmic acid in the epithelial cells are not free fatty acid. The free fatty 

 acids only become emulsified when melted, and as pure palmitic acid 



1 Virchow's Archiv, 1868, Bd. xliii. S. 271 ; 1872, Bd. Ivi. S. 211. 



2 Centralbl.f. d. med. Wissensch., Berlin, 1876, S. 851. 



3 Arch. f. d. ges. PhysioL, Bonn, 1879, Bd. xx. S. 255. See also v. Krehl, Arch. f. 

 Anat. u. PhysioL, Leipzig, 1890, Anat. Abth., S. 97. 



4 In thus showing the formation of fat from fatty acid alone, Will anticipated I. Munk, 

 but to Munk belongs the merit of clearly showing from the chemical standpoint that the 

 organism, probably the epithelial cells, can furnish the glycerin radicle for the synthesis 

 of neutral fats from the fatty acids. 



5 Sitzungsb. d. Berl. physiol. Gesellsch., March 1879 ; Virchow's Archiv, 1880, Bd. Ixxx. 

 This was a re-discovery of a fact known to Marcet many years previously, see p. 444. 



