SOL UTION THEORIES OF FA T ABSORPTION. 451 
converted into fats somewhere on their way from the intestine to the 
thoracic duct. He is hence of the opinion that in the norma] course of 
digestion a considerable bul indeterminate amount of fat may be 
absorbed in the form of emulsified fatty acids. 
Munk's experimental results as to the absorption and synthesis 
(luring 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 sane' 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. Radziejewski 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 Grunhagen'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 Archie, 1868, Bd. xliii. S. 271 ; 1872, Bd. Ivi. S. 211. 
2 Centralbl. f. d. med. Wissensch., Beidin, 1876, S. 851. 
3 Arch. f. d. ges. Physiol., Bonn, 1879, Bd. xx. S. 255. See also v. Krehl, Arch. f. 
Aunt. 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. Perl, physiol. Gesellsch., March 1879 ; Virchow's Archiv, 1880, Bd. lxxx. 
This was a re-discovery of a fact known to Marcet many years previously, see p. 444, 
