394 VETEEINARY PHYSIOLOGY 



two of a fast, the individual goes on using proteins and fats at 

 something like the same rate as he did while taking food, but 

 that gradually he uses less and less protein each day. This is 

 well shown in the case of Succi, who underwent a fast of 

 thirty days. 



Day of Fast. Protein used iu Grms. Fat used. 



1st 104 Not estimated. 



10th 51 170 



20th 33 170 



29th 31 163 



It is from the stored fats that the energy is chiefly derived, 

 and the result of this is that before death the fats of the body 

 are largely used up. The protein-containing tissues waste 

 more slowly and waste at different rates, the less essential 

 being used up more rapidly than the more essential, which, in 

 fact, live upon the former. In cats deprived of food till death 

 supervened the heart and central nervous system had hardly 

 lost weight : the bones, pancreas, lungs, intestines, and skin 

 each had lost between 10 to 20 per cent, of their weight, the 

 kidneys, blood, and muscles between 20 to 30, and the liver 

 and spleen between 50 to 70. 



The rate of waste during a fast depends upon the amount of 

 energy required, and it is therefore increased by muscular work 

 and by exposure to cold. When a man is kept quiet and 

 warm and supplied with water, a fast of thirty days may in 

 some cases be borne without injury. 



3. Effect of Feeding 



When food is given to a fasting animal or man, the first 

 effect is to increase the rate of wasting by calling into action 

 the muscles and glands concerned in digestion. The result is 

 an immediate increase in the excretion of nitrogen and carbon, 

 indicating an increased breaking down of proteins and fats. 

 It has been found that in the dog a diet of white bread and 

 butter increased the metabolic processes by an amount equiva- 

 lent to about 1 per cent, of the energy value of the diet. For 

 this reason, to give an animal which is fasting a diet containing 

 just the amount of nitrogen and of carbon which the animal is 



