EFFECT OF MUSCULAR WORK AND TEMPERATURE. 813 



According to these results, the greatest absolute loss was in the 

 muscles (429 gins.), while the greatest percentage loss was in the fat 

 (97 per cent.), which had practically disappeared from the body. 

 It is very significant that the central nervous system and the heart, 

 organs which we may suppose were in continual activity, suffered 

 practically no loss of weight: they had lived at the expense of the 

 other tissues. We must suppose that in a starving animal the fat 

 and the proteid materials, particularly in the voluntary muscles, 

 pass into solution in the blood, and are then used to nourish the 

 tissues generally and to supply the heat necessary to maintain the 

 body temperature. Examination of the excreta in starving ani- 

 mals has shown that a greater quantity of proteid is destroyed dur- 

 ing the first day or two than in the subsequent days. This fact 

 is explained on the supposition that the body is at first richly sup- 

 plied with "circulating proteid" derived from its previous food, and 

 that after this is metabolized the animal lives entirely, so far as 

 proteid consumption is concerned, upon its "tissue proteid." If 

 the animal remains quiet during starvation, the amount of nitrogen 

 excreted daily soon reaches a nearly constant minimum, showing 

 that a practically constant amount of proteid (together with fat) 

 is consumed daily to furnish body heat, and probably to repair 

 tissue waste in the active organs, such as the heart. Shortly before 

 .death from starvation the daily amount of proteid consumed may 

 increase, as shown by the larger amount of nitrogen eliminated. 

 This fact is explained by assuming that the body fat is then exhausted 

 and the animal's metabolism is confined to the tissue proteids alone. 

 The general fact that the loss of proteid is greatest during the first 

 one or two days of starvation has been confirmed recently upon men, 

 in a number of interesting experiments made upon professional 

 f asters. For the numerous details as to loss of weight, variations 

 of temperature, etc., carefully recorded in these latter experiments, 



