CHAPTER LXIII 

 STARVATION 



In order to furnish us with a standard with which we may compare 

 other conditions, we shall first of all study the metabolism during starva- 

 tion. A valuable chart compiled from observations made in the Carne- 

 gie Institution of Washington on a man who fasted for thirty-one days 

 is reproduced in Fig. 182. 



The Excretion of Nitrogen. When an animal is starved, it has to 

 live on its own tissues, but in doing so it saves its protein, so that the 

 excretion of nitrogen falls after a few days to a low level, the energy 

 requirements being meanwhile supplied, so far as possible, from stored 

 carbohydrate and fat. Although always small in comparison with fat, 

 the stores of carbohydrate vary considerably in different animals. They 

 are much larger in man and the herbivora than in the carnivora. Dur- 

 ing the first few days of starvation it is common, in the herbivora, to find 

 that the excretion of nitrogen is actually greater than it was before 

 starvation, because the custom has become established in the metabolism 

 of these animals of using carbohydrates as the main fuel material, so 

 that when carbohydrates are withheld, as in starvation, proteins are 

 used more than before and the nitrogen excretion becomes greater. We 

 may say that the herbivorous animal has become carnivorous. The same 

 thing may occur in man when the previous diet was largely carbohy- 

 drate; thus, almost invariably in man the nitrogen output is larger on 

 the third and fourth days of starvation than on the first and second. 



Another factor influencing the nitrogen excretion during the early 

 days of the fast is the amount of previous intake of nitrogen; the greater 

 this has been, the greater the excretion. By the seventh day, however, a 

 Uniform output of nitrogen will usually be reached irrespective of the 

 individual's protein intake. During the greater part of starvation, most 

 of the energy required to maintain life is derived from fat, as little as 

 possible being derived from protein. This type of metabolism lasts until 

 all the available resources of fat have become exhausted, 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 indicates that all the 

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



566 



