FASTING METABOLISM 55 



greater the part played by the fat in the production 

 of heat. 



It has been found with a dog experimented upon 

 in various stages of fatness that when starving the 

 production of heat was divided between the protein 

 and the fat in the following proportions 

 Condition of Heat furnished by 



the animal. flesh (protein) . fat. 



Fat . . . 6-1% . . 93-9% 

 Lean . . 14-4% . . 85-6% 



Very lean . . 167% . . 83-3% 



During the period of starvation the fat disappears 

 by degrees, and then the body proteins are called 

 upon to furnish heat. However fat though the 

 animal may be, the protein metabolism never com- 

 pletely ceases, for protein plays a part which cannot 

 be performed by fat. 



Observations on fasting animals give a clearer 

 insight into the metabolism of the body than can 

 be the case where food is given, and therefore they 

 have found a place here. 



(2) Insufficient feeding. 



In the preceding section it has been shown that a 

 starving animal lives upon the materials of its body. 

 The amount of heat which it gives out serves as an 

 exact measure of the requirements of the body in 

 material and energy. If such an animal is given 



