SYNTHESIS OF FATS ACCOMPANYING INTESTINAL ABSORPTION 27 
they do not show accurately the amount of free fatty acid formed, they very 
conclusively prove that no neutral fat is formed. For, while a considerable amount of 
soap is dissolved out from the dried extracts in the second method, which, if the 
attempt be made to obtain the amount of neutral fat, as in Ewald and Hamburger's 
calculations, by merely subtracting the amount of free fatty acid from the total 
ethereal extract, gives rise to the fallacious result that a considerable synthesis of 
neutral fat has taken place ; in using the first method, namely, that of extracting 
without previous evaporation to dryness, practically no soap is dissolved by the ether, 
and the subsequent titration gives almost theoretical values for oleic acid, showing 
that the entire ethereal extract consists of fatty acid, and that no neutral fat is 
present. 
If any neutral fat whatever had been formed by the previous digestion with 
the extracts of intestinal mucosa and other tissues employed, it would undoubtedly 
have been present in the ethereal extract, because olein is practically insoluble in water, 
but soluble in all proportions in ether, and hence would have been dissolved out even 
more readily than oleic acid, which has a slight solubility in water. 
Hamburger, although he did not proceed to the direct determination of the 
neutral fat in the extracts he obtained, was aware of the solubility of soaps in ether, 
and sought to equalize this by adding, after evaporation, soaps to his controls. Even 
with this precaution, he found a greater weight of ethereal extract, after deducting 
free fatty acid, in those portions to which the soap had been added before boiling, and 
ascribed this excess to neutral fat. 
A repetition of this procedure in the present series of experiments, did not 
give, however, a like result, the difference in weight was very slight, and in one case 
was in favour of the portion to which the soap had been added before digestion, and 
in the other, in favour of that to which the soap had been added after digestion. 1 
Hamburger's own results, moreover, are not uniform, for while a greater 
weight was found in some experiments, no appreciable change was found in others. 
Hamburger supposes that the negative result is due to re-conversion into 
fatty acid during prolonged digestion of the neutral fat first formed. 
Supported by the results of the method of direct estimation of the neutral fat, 
as well as by the results obtained by duplicating Hamburger's own method, we are 
of the opinion that the positive results of Hamburger are due to dissolved soap, 
which varied in amount in the different experiments. 2 
The hydrolysis of sodium oleate and accompanying liberation of oleic acid, 
above alluded to, by extracts of pancreas, lymphatic glands, and intestinal mucosa, is 
remarkable in that it is not completely stopped by previous boiling of the extracts. 
In most cases the extent of hydrolysis is lessened by boiling, as will be seen by 
1. See Experiment!, I and 2, Series ii. 
2. It may be mentioned that Hamburger used sapo medicatus, while Sodium Oleate was used for the experiments 
described in this paper. 
