FORMATION OF FAT FROM PROTEINS. 535 



formation of fat from protein took place, but rather a fat migration 

 (ROSENFELD). 



Another more direct proof of the formation of fat from proteins 

 has been given by HOFMANN. He experimented with fly-maggots. 

 A number of these were killed and the quantity of fat determined. The 

 remainder were allowed to develop in blood whose proportion of fat 

 had been previously determined, and after a certain time they were killed 

 and analyzed. He found in them from seven to eleven times as much 

 fat as was contained in the maggots first analyzed and the blood taken 

 together. PFLUGER 1 has made the objection that a considerable number 

 of lower fungi develop in the blood under these conditions, in whose 

 cell-body fats and carbohydrates are formed from the different con- 

 stituents of the blood and their decomposition products, and that these 

 serve as food for the maggots. 



WEINLAND 2 has observed the formation of higher non-volatile fatty 

 acids in the Calliphora larvae when they were rubbed to a homogeneous 

 paste after the addition of Witte's peptone. This experiment shows a 

 formation of fat from protein, but cannot be considered as quite con- 

 clusive. 



As a more convincing proof of fat formation from proteins, the investi- 

 gations of PETTENKOFER and VOIT are often quoted. These investi- 

 gators fed dogs with large quantities of meat containing the least possible 

 proportion of fat, and found all of the nitrogen in the excreta, but only 

 a part of the carbon. As an explanation of these conditions it has been 

 assumed that the protein of the organisms splits into a nitrogenized 

 and a non-nitrogenized part, the former changing into the nitrogenized 

 final product, urea, and like products, and the other part, on the contrary, 

 being retained in the organism as fat (PETTENKOFER and VOIT). 



PFLUGER has arrived at the following conclusion by an exhaustive 

 criticism of PETTENKOFER. and VOIT'S experiments and a careful recal- 

 culation of their balance-sheet; that these very meritorious investiga- 

 tions, which were continued for a series of years, were subject to such 

 great defects that they are not conclusive as to the formation of fat 

 from proteins. He especially emphasizes the fact that these investigators 

 started from a wrong assumption as to the elementary composition of 

 the meat, and that the quantity of nitrogen assumed by them was too 

 low and the quantity of carbon too high. The relation of nitrogen to 

 carbon in meat poor in fat was assumed by VOIT to be as 1:3.68, 

 while according to PFLUGER it is 1:3.22 for fat-free meat after deducting 

 the glycogen, and according to RUBNER 1:3.28 without deducting the 

 glycogen. On recalculation of the figures, using these coefficients, PFLUGER 



1 See Rosenfeld, Fettbildung, Ergebnisse der Physiologic, 1, Abt. 1. 



2 Zeitschr. f. Biol., 51. 



