FORMATION OF FAT FROM PROTEIN 407 



with Pettenkofer in a series of extensive studies developed 

 the theory that protein is the principal source of fat in the 

 living body. For decades metabolic physiology remained 

 under the domination of this doctrine, supported as it was 

 by the great authority of its founders, until it was over- 

 thrown by the ponderous opposition of E. Pfliiger. " These 

 celebrated experiments of Voit and Pettenkofer," wrote 

 Pfliiger at the beginning of the nineties, " prove nothing for 

 the formation of fat from protein. For the computations of 

 these investigators, as here involved, are really the result of 

 a mistaken assumption as to the elementary composition of 

 lean meat, which Voit adopted, not after analysis, but from 

 his personal judgment, in contravention of analyses of other 

 investigators generally regarded as reliable, and in fact con- 

 trary to the results of his own analyses. It is on such a 

 foundation that the modern superstructure of metabolism 

 rests for the majority of physiologists." In answer to these 

 ideas the Voit school set about energetically to defend itself ; 

 and in particular E. Voit, M. Cremer and M. Gruber brought 

 forward new arguments for the retention of a carbon residium 

 after meat consumption which did not seem covered by the 

 carbohydrate in the food, and which, therefore, was held to 

 indicate a formation of fat from protein. Pfliiger invariably 

 returned to the fray with new objections, of the correctness 

 of which different opinions might be, and in fact were held. 

 To-day the whole question has shifted; since, as has been 

 stated, we must necessarily accept the formation of sugar 

 from protein as a settled fact, and cannot possibly doubt 

 that fat is formed from sugar. The logical conclusion, 

 therefore, follows that it must be granted that in the living 

 body fat may be formed from protein. It is another ques- 

 tion, of course, whether under practical conditions this 

 possibility becomes an actuality. When very large amounts 

 of protein are fed one would probably always contemplate 

 such a result. Magnus-Levy, as well-informed in the funda- 

 mental points as he is an objective observer in the subject of 



