568 METABOLISM 



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 liq- 

 uidation of permanent assets. But these assets, as represented by pro- 

 tein, 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 starva- 

 tion for a longer time. The premortal rise is, however, not prevented by 

 feeding oil, which would seem to indicate that death may be due not so 

 much to the absence of fuel as to serious nutritional disturbance of es- 

 sential organs; e. g., there may be no available material to supply the 

 glands of internal secretion with the building stones they must have 

 (see page 580). 



Not only is there this general saving of protein during starvation, 

 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 un- 

 dergoes 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 accounted 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 transformation is sine qua non of life. The vital 

 organs live at the expense of those whose functions are accessory. 



The energy output per square meter of body surface steadily declines. 

 In the man examined by Benedict, it was 958 C. per square meter of 

 surface at the end of the first twenty-four hours, but only 737 on the 

 thirty-first day of the starvation period. The oxygen intake and carbon- 

 dioxide output correspondingly diminish. 



The behavior of the nitrogenous metabolites in the urine is of par- 

 ticular interest, the following facts being of significance: Urea nitrogen 

 relatively falls and NH. ? - N rises. For example, on the last day of feeding 

 the percentage output of NH 3 - N in relation to total nitrogen was 3.16 ; 

 on the eighth day of the fast it was 14.88 (Cathcart). 2 Acidosis is the 

 cause. The total amount of creatinine and creatine shows only a slight 

 fall, but creatinine relatively decreases and creatine increases (Cathcart). 

 Since creatine is a substance peculiar to muscle tissue, it is possible by 



