METABOLISM, NUTRITION AND DIETETICS 457 



in the form of fat ; for lean meat contains but a trifling quantity of 

 carbon in any other proximate principle than proteid, and the non- 

 proteid carbon of the animal body is only to a very small extent 

 contained in carbo-hydrates or other substances than fat. 



For example, in an experiment of Pettenkofer and Voit on a 

 34-kilo dog in nitrogenous equilibrium, with a diet of 2,000 grammes 

 of lean meat, the animal on the first day 



Grammes. Grammes. 



Took in in the food - 68'o N 250*4 C 



( urine - - 66*5 N 39-9 C 



Gave out in < fasces - - 1*4 9*2 



(respiration - o 158*3 



679 207-4 



Difference - +0*1 N -f43'o C 



Here the nitrogen of the body remained unaltered, but carbon 

 was put on to the extent of 43 grammes, or 17 per cent, of the 

 amount in the food, representing about 58 grammes of fat. It is 

 very unlikely that the whole of this carbon, or even the greater part of 

 it, could have been retained as glycogen. For 43 grammes of carbon 

 correspond to nearly 100 grammes of glycogen, or nearly 3 grammes 

 per kilo of body-weight ; and there is nothing to indicate that such 

 an increase in the glycogen store ever takes place in a single day. 



Some exact quantitative proofs of the conversion of proteids 

 into fat have been quoted. Qualitative indications of its 

 possibility and of its actual occurrence are numerous. Such 

 are the readiness with which fatty degeneration occurs in the 

 tissues in pathological states for example, after poisoning 

 with phosphorus, arsenic, or antimony, the accumulation of 

 fat between the hepatic cells caused by phloridzin, which, as 

 we know, hastens the disintegration of proteids ; the forma- 

 tion of adipocere (a cheesy substance, rich in fatty acids 

 united with calcium or ammonium) sometimes seen in dead 

 bodies which have remained a long time under water or in 

 moist graveyards; the formation of fat in the cells of the 

 sebaceous glands ; and the transformation of the cell-sub- 

 stance of the mammary glands into the fat of milk. This 

 last case is of great practical importance, for it explains the 

 rule which experience has taught, that a woman during lacta- 

 tion requires an excess of proteids in her food corresponding 

 not only to the proteids, but also to the fat given off in the 

 milk. 



(2) From Carbo-hydrates. It has been found that the 

 addition of proteid to a diet of fat, and especially to a diet 



