1 82 PHYSIOLOGICAL CHEMISTRY 



absorbed. He believes that saponification is a necessary preliminary 

 to absorption. 



It has been shown 1 that the common food fats are from 93 to 98 

 per cent utilized by the normal human body. 



The fat distributed throughout the animal body is formed partly 

 from the ingested fat and partly from carbohydrates and the "carbon 

 moiety" of protein material. The formation of adipocere 2 and the 

 occurrence of fatty degeneration are sometimes given as proofs of the 

 formation of fat from protein. This is questioned by many investiga- 

 tors. Rather more satisfactory and direct proof of the formation of fat 

 from protein material has been obtained by Hofmann in experimentation 

 with fly-maggots. The normal content of fat in a number of maggots 

 was determined and later the fat content of others which had developed 

 in blood (84 per cent of the solid matter of blood plasma is protein 

 material) was determined. The fat content was found to have in- 

 creased 700 to 1 100 per cent as a result of the diet of blood proteins. 



FIG. 57. MUTTON FAT, (Long.} 



The celebrated experiments of Pettenkofer and Voit, however, have 

 furnished what is, perhaps, the most substantial positive evidence of 

 the formation of fat from protein. These investigators fed dogs large 

 amounts of lean meat, daily, and through examination of urine, feces and 

 expired air were enabled to account for only part of the ingested carbon, 

 although obtaining a satisfactory nitrogen balance. The discrepancy 

 in the carbon balance was explained upon the theory that the protein of 

 the ingested meat had been split into a nitrogenous and a non-nitroge- 

 nous portion in the organism, and that the non-nitrogenous portion, the 

 so-called "carbon moiety" of the protein, had been subsequently trans- 

 formed into fat and deposited as such in the tissues of the organism. 



1 Holmes and Deuel: Jour. Biol. Chem., 41, 227, 1920. 



2 A very complete analysis of adipocere was reported by Ruttan and Marshall before 

 the Society of Biological Chemists, Boston, Dec. 27, 1915. V 



