STARVATION. 93 



as possible being derived from protein. This type of metabolism 

 lasts until all the available resources of fat have become ex- 

 hausted, when a more extensive metabolism of protein sets in 

 with the consequence that the nitrogen excretion rises. This is 

 really the harbinger of death it is often called the premortal 

 rise in nitrogen excretion. It means that all the ordinary fuel 

 of the animal economy has been used up, and that it has become 

 necessary to burn the very tissues themselves in order to obtain 

 sufficient energy to maintain life. Working capital being all 

 exhausted, an attempt is made to keep things going for a little 

 longer time by liquidation of permanent assets. But these assets, 

 as represented by protein, are of little real value in yielding the 

 desired energy because, as we have seen, only 4.1 calories are 

 available against 9.3, obtainable from fats. These facts explain 

 why during starvation a fat man excretes daily less nitrogen 

 than a lean man, and why the fat man can stand the starvation 

 for a longer time. 



Not only is there this general saving of protein during star- 

 vation, but there is also a discriminate utilization of what has 

 to be used by the different organs according to their relative 

 activities. This is very clearly shown by comparison of the loss 

 of weight which each organ undergoes during starvation. The 

 heart and brain, which must be active if life is to be maintained, 

 lose only about 3 per cent of their original weight, whereas the 

 voluntary muscles, the liver and the spleen lose 31, 54 and 67 

 per cent, respectively. No doubt some of this. loss is to be ac- 

 counted for as due to the disappearance of fat, but a sufficient 

 remainder represents protein to make it plain that there must 

 have been a mobilization of this substance from tissues where it 

 was not absolutely necessary, such as the liver and voluntary 

 muscles, to organs, such as the heart, in which energy transfor- 

 mation is sine qua non of life. The vital organs live at the ex- 

 pense of those whose functions are accessory. 



When we compare the excretion of carbon dioxide from day 

 to day during starvation, it will be found to remain practically 

 constant, when calculated for each kilogram of body weight. The 

 same is true for the calorie output. Certain unusual substances 



