108 PRINCIPLES OF ANIMAL NUTRITION. 
tending to show that the proteids were not without influence on 
fat-production. 
As early as 1745 R. Thomson,* in experiments on milch cows, 
noted an apparent connection between the supply of proteids in 
the food and the production of butter. 
Hoppe ¢ in 1856 interpreted the results of an experiment in 
which a dog was fed lean meat with and without the addition of 
sugar as showing a formation of fat from proteids. The same 
author { in 1859 claimed to have shown a slight formation of fat 
from casein in milk exposed to the air, and this was confirmed later 
by Szubotin.§ The latter author, and also Kemmerich,| and later 
Voit,{ experimented upon the production of milk-fat by dogs. 
Their results, while indicating the possibility of a formation of fat 
from proteids, were indecisive. 
PretreNKOFER & Vorr’s EXPERIMENTS.—Carl Voit, however, 
was the first to distinctly champion the new theory, and aside from 
certain confirmatory facts,** such as the formation of fatty acids in 
the oxidation of proteids, the formation of adipocere, the alleged 
formation of fat from proteids in the ripening of cheese and in the 
fatty degeneration of muscular tissue, especially in cases of phos- 
phorous poisoning,—facts not all of which are fully established and 
whose importance in this connection has probably been over- 
estimated,—the evidence bearing on the question of the formation of 
fat from proteids has been until recently largely that supplied by 
the famous researches of Pettenkofer & Voit tt at Munich. 
In these experiments a dog weighing about 30 kgs. was fed 
varying amounts of prepared lean meat from which fat, connective 
tissue, etc., had been removed as completely as was possible by 
mechanical means. The material thus prepared, while still con- 
taining small amounts:of fat, etc., was as near an approach to an 
exclusively proteid diet as was practicable, it having been found 
impossible to successfully carry out feeding experiments with pure 
* Ann, Chem. Pharm., 61, 228. t Virchow’s Archiv, 17, 417. 
} Virchow’s Archiv, 10, 144 § Ibid., 86, 561. 
|| Wolff, Ernahrung Landw. Nutzthiere, p. 351. 
q Zeit. f. Biol., 5, 136. 
** Compare Voit’s summary in 1869, Zeit. f. Biol., 5, 79-169. 
ttAm. Chem. Pharm., II, Suppl. Bd., pp. 52 and 361; Zeit. f. Biol., 5, 
106; 7, 433. 
