THE METABOLIC REQUIREMENTS OF THE BODY 1053 



reptiles and amphibia not until after many months and possibly a 

 year. Secondly, it may readily be gathered that the production of 

 heat in starving animals must be greatly reduced. Thus, the profes- 

 sional faster Cetti 1 required on the first day only 32.4 calories for each 

 kilogram of his body-weight and, on the fifth day, only 30.0 calories. 

 Similar values have been found by Tigerstedt. 2 In accordance with 

 Rubner 3 and Magnus-Levy, 4 this loss of energy is only 7 to 15 per 

 cent, lower than that in a person ingesting a moderate amount of food. 



The course of the elimination of nitrogen during periods of star- 

 vation is closely dependent upon the condition of the animal at the 

 time of withholding the food. If the animal has been accustomed to 

 ingest large amounts of protein material, its protein-catabolism will 

 be rather high during the first few days of the period of starvation, but 

 a uniformly low output of nitrogen will have been reached at the end 

 of about a week. Meanwhile, its store in glycogen will have become 

 exhausted, while its fats will have been drawn upon incessantly to 

 shield its proteins. As soon as all the available fat has become ex- 

 hausted, a more intense metabolism of the proteins sets in, in conse- 

 quence of which the output of nitrogen is increased. This 'premortal 

 rise in the excretion of nitrogen constitutes an unfavorable diagnostic 

 sign, because it indicates that the ordinary fuel of the animal has been 

 thoroughly depleted. 



In the herbivora, conditions are somewhat different, because these 

 animals possess a large store of glycogen. Thus, it is commonly found 

 that their output of nitrogen is considerably increased during the first 

 days of the period of starvation, because since they have been accus- 

 tomed to use carbohydrates as their chief fuel, the sudden withdrawal 

 of this foodstuff forces them to fall back upon their store of proteins. 

 A very similar reaction takes place in men who have been accustomed 

 to eat large amounts of carbohydrates. In both instances, therefore, 

 starvation changes the metabolism into a type more nearly like that 

 of the carnivorous animals. 



The ingo of oxygen and outgo of carbon dioxid soon reach a minimal 

 value. Urea nitrogen falls and NH 3 N rises, but the total amount of 

 creatinine and creatine, which form peculiar derivatives of the meta- 

 bolism of muscle tissue, is not changed materially. The excretion of 

 the purines is decreased at first and then increased, owing, in all 

 probability, to the steady destruction of the nuclear material. As 

 far as the relation of the sulphur to the nitrogen is concerned, it is to 

 be noted that their ratio is at first as 17N: IS, and later on, as 14.5N: IS. 

 If anything, these values suggest that the principal source of protein 

 during the later stages of starvation is the protein material of muscle 

 tissue. 



1 Virchow's Archiv, cxxxi, 1893; also: Benedict, Carnegie Inst. of Washington, 

 No. 126, 1910. 



2 Skand. Archiv fur Physiol., vii, 1897, 29. 



3 Gesetze des Energieverbr., Leipzig, 1902. 



4 Pfliiger's Archiv, Iv, 1894, 96. 



