24 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
Much more recently, Hamburger, 1 working chiefly with the large intestine, 
has brought forward evidence from a large number of experiments, claiming to show 
that synthesis of neutral fats can be brought about in vitro, by the separated intestinal 
mucosa. 
Neither Ewald nor Hamburger worked with extracts free from cells, and 
their methods of working save in experimental details were the same, so that both 
sets of results can be conveniently discussed together. 2 
The method was essentially that of digesting a mixture of soap and glycerine 
in solution, in presence of intestinal mucosa finely minced up, for a variable period, 
obtaining an ethereal extract, and determining the amount of fatty acid in this by 
titration against a standard alkali. 
The difference between the weight of the total ethereal extract and the weight 
of free fatty acid was taken to be neutral fat, and the difference between this figure, 
in the case of portions to which soap and glycerine had been added, and controls in 
which no soap and glycerine were added, was taken to represent neutral fat which had 
been formed during the experiment. 
No direct determinations- were made by saponification with alkali of the 
amount of neutral fat formed. Now, had such a course been taken in the experiments 
detailed later in this paper, as a perusal of the figures will show, a fallacious conclusion 
that fat was synthesized would in some cases have been the result. But the direct 
determinations show that this is not the case, and hence that probably in Ewald 
and Hamburger's experiments, also, the supposed fat synthesized was in reality soap 
dissolved by the ether used as an extractive. 
In any case, the present experiments show no appreciable synthesis of neutral 
fat from soap and glycerine, either by the fresh intestinal mucosa or by cell-free extracts 
of it. 
Other workers have turned from the direct synthesis of neutral fats and 
attempted instead to draw analogies from the synthesis of simpler esters. 
Thus, Kastle and Loevenhart 3 digested a mixture of dilute butyric acid and 
ethyl alcohol with a fresh aqueous extract of pancreas, and were able to detect ethyl 
butyrate by its odour, and on the larger scale were able to obtain a few drops of a 
light oil with the odour and general properties of that ester. The reaction did not 
occur when boiled pancreas was used, and since, on the other hand, lipase can also be 
employed to convert ethyl-butyrate into butyric acid and ethyl alcohol, it becomes 
evident that the action is a reversible one. 
1. Arch.f. Physiol., 1900, S. 4.33. 
2. The only essential difference was, that Hamburger evaporated to dryness before extracting with ether, while Ewald first 
filtered after digestion and then evaporated the filtrate to a small volume, and extracted with ether, adding this to an ethereal 
extract of the residue from filtration. 
3. American Chemical Journal, 1900, Vol. xxiv, p. 491. 
