292 THE SOURCE OF BODY FAT 



Pfliiger suggests that amido-acids might be retained, such as tyrosin 

 the degradation products of pancreatic digestion. This might 

 easily result, considering the large amount of proteid fed. Secondly, 

 in the elementary analyses of lean meat by Rubner and Argutinsky, 

 &c., the ether method of extraction was used for determining the 

 amount of fat present. Now, Rosenfeld's method of boiling the 

 tissue with alcohol and then extracting with chloroform may yield 

 40 per cent, more extract than other methods. On the other 

 hand, this method extracts more than fat. While there is 

 this doubt as to the amount of fat in the meat, the figures quoted 

 above can prove nothing as to the formation of fat from proteid. 

 M. Kumagawa selected two similar dogs of the same litter, and 

 robbed them of their depot fat to the utmost by twenty-four days' 

 starvation. He then killed and analysed one, while the other he 

 fed with lean horse-flesh to such a degree that it an 8 kg. dog 

 consumed 49 kg. in 49 days, a diet equivalent to 133 Cal. per kg. 

 of live weight. The dog increased from 6*08 to 10 kg. In the 

 control dog there was 120 grm. fat, in the other 1087-7 grm. The 

 amount of fat put on then was assumed to be 928 grm. In the 

 meat absorbed there was 1084 grm. fat, and 356 grm. glycogen 

 in other words, enough to cover the total onput of body fat, 

 so there was no evidence of the formation of fat from proteid 

 here. 



We must conclude, then, that the metabolic evidence of the 

 formation of fat from proteid is at present lacking. It is impossible 

 to feed an animal on pure proteid alone, such as casein, and it is 

 exceedingly difficult to determine with any degree of accuracy the 

 amount of fat in lean meat. If it were possible to do this, the 

 question as to whether glycogen or fat is stored could be settled by 

 an exact estimation of the oxygen exchange, since the difference in 

 the oxygen content of fat and glycogen is very great. In support 

 of the view that fat can be formed from proteid is the fact that 

 glycogen can be formed from proteid, and that fat can be formed 

 from carbohydrate. 



Attempts have been made to prove the origin of fat from 

 proteid in the formation of adipocere, the ripening of cheese, the 

 formation of fat in fly-maggots fed on blood, and the formation of 

 milk, in the fatty degeneration which occurs in phosphorus poison- 

 ing, &c. 



