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THE SOURCE OF BODY FAT 



THE SOURCE OF BODY FAT Is IT FORMED FROM PROTEID 1 



The physiologists of the earlier part of the nineteenth century 

 held that animal fat was food fat which had escaped oxidation 

 and been deposited in the tissues. Liebig taught the origin of fat 

 from carbohydrate. After much debate Voit introduced the 

 doctrine that proteid is the chief source of fat, and this became 

 generally accepted in 1880 and remained so until Pfltiger in 1891, 

 in a trenchant criticism of Voit's experiments, proved that the 

 latter were inadequate. Pettenkofer and Voit's conclusion, said 

 Pfltiger, were based upon an erroneous calculation of the elemen- 

 tary composition of the lean meat on which their test dogs were 

 fed. The percentage composition which Voit chose as correct was 

 not based on analysis but on opinion, and is in truth in opposition 

 to the analysis of other workers. Pettenkofer and Voit fed dogs 

 on great quantities of lean meat and found in the excreta all the 

 N but not all the C which they calculated to be in the food. 

 The amount of C retained in the body was, they said, too much 

 to be regarded as stored glycogen. 



The proportion of C to N in muscle proteid Voit chose as 

 1:34, while Rubner as the result of analyses put it at 1 : 3*28, 

 and even this figure must receive a slight correction for the small 

 per cent, of glycogen present in muscle. The carbon in the urine 

 was estimated by Voit from the amount of N on the assumption 

 of the ratio being 1 : 0*60 while it should bs 1 : 0*67. Using these 

 corrections, Pfluger has recalculated Voit's experiment and found 

 no proof of fat formation on a diet of lean meat, thus : 



These were the figures in one typical experiment where the 

 uptake was 2500 grm. of flesh : 



