200 ORGANIC AGRICULTURAL CHEMISTRY 



supply energy, it is deposited as body fat. This body fat may 

 later be drawn upon to supply energy, in which case it is recon- 

 verted into the soluble form and again enters the blood of the 

 muscle cells and is oxidized. This is proved by experiment 

 upon fasting or hibernating animals in which body fat is lost 

 in proportion to the energy set free. 



Conversion of Fats into Carbohydrates. — There is still a 

 question as to whether body fat, or even the first formed fat in 

 blood plasma, is burned directly as fat or is first converted into 

 glucose. Experimental evidence seems to indicate, however, 

 that while body fat may be first converted into glucose and 

 then oxidized, yet directly absorbed food fat is undoubtedly 

 burned in the body, that is, in the muscle cells, without being 

 first converted into glucose. Such a conversion of food fat into 

 glucose preceding oxidation would result in the loss of a con- 

 siderable proportion of the fuel value of the fat, whereas experi- 

 ments have shown that almost the full amount of the fuel value 

 of fat food is utilized as energy in the animal body. 



We have, nevertheless, almost as conclusive evidence that 

 body fat is at least possible of conversion into glucose. In 

 fasting or hibernating animals the blood maintains its constant 

 amount of glucose, viz. o.i per cent. This constant supply of 

 glucose in the blood could only be maintained under these con- 

 ditions by the conversion of body fat into glucose. Also in 

 these cases the respiratory quotient has been found to be below 

 0.7, the value of the quotient when fat alone is oxidized. Such 

 a value for the respiratory quotient must mean that fat is being 

 converted into glucose, just as the value greater than i .0 means 

 that carbohydrate is converted into fat, as previously dis- 

 cussed. It has also been shown that the glycogen content of 

 the body has increased, in the case of hibernating animals, at 

 the expense of body fat. This conversion of fats into carbo- 

 hydrates is thought to take place in the liver, and as this organ 

 contains a very large number of different enzymes such a trans- 

 formation is not improbable. It is possible that the formation 

 of carbohydrate from fat takes place only from the glycerol 



