THE RELATIONS OF METABOLISM TO FOOD-SUPPLY. 173 
account be taken of this fact the teachings of Weiske & Wildt’s 
experiment cited above are exactly reversed and show a formation 
of fat from carbohydrates. A consideration of the same fact, of 
course, tends to make the results of all similar experiments, includ- 
ing those on milch cows, more favorable to the carbohydrates. 
Still further, it is doubtful whether 100 parts of proteids can 
actually yield 51.4 parts of fat. The latter number was computed 
by Henneberg from the elementary composition of proteids and of 
urea to be the maximum amount obtainable. Zuntz,* however, 
has called attention to the fact that if the proteids actually split up 
in the manner which Henneberg’s calculation supposes, the products 
must contain all the potential energy of the original material, so 
that none can be given off during their cleavage. This is a process 
wholly without analogy in the animal body, and, to say the least, 
very improbable. It would seem then, that even if we still hold to 
a formation of fat from proteids, we must considerably reduce our 
estimate of its amount. 
Later Fattening Experiments.—All these considerations tend to 
strengthen the belief that fat is formed from carbohydrates, and 
more recent experiments have demonstrated that such is the fact. 
Henneberg, Kern, & Wattenberg,f in experiments undertaken to 
determine the rate of gain and the composition of the increase of 
fattening sheep, and conducted substantially like those of Lawes 
& Gilbert on swine, were the first to furnish proof of the formation 
of fat from carbohydrates by ruminants. Wolff{ having pointed 
out that their results demonstrated that fact, Henneberg discussed 
this feature of the experiments in a later publication.§ Regarding all 
the digested ether extract of the food as pure fat, and assuming that 
all the digested nitrogenotis matters were true proteids capable of 
yielding 51.4 per cent. of fat, he obtained the results given on p. 174. 
Forty-two per cent. more fat was produced than could be accounted 
for by the fat and proteids of the food, even on the extreme 
assumptions made. Furthermore, not only did some of the 
nitrogenous substances of the food undoubtedly consist of non-pro- 
* Landw. Jahrb., 8, 96. 
¢ Jour. f. Landw., 26, 549. 
t Landw. Jahrb., 8, I. Supp., 269. 
§ Zeit. f Biol , 17, 345. 
