4OO PHYSIOLOGICAL CHEMISTRY. 



This number of calories must be taken from the net produced 

 calories to obtain the heat radiated or otherwise lost by the 

 body. We have then this difference : 



2,686.200 

 630,460 



2,055,740 



That is, something over 2,000,000 calories are dissipated by 

 radiation. 



HEAT RADIATION WHEN WORK IS DONE. 



All these calculations are based on the assumption that no 

 mechanical work is being done by the person under observa- 

 tion, or if done it is finally all converted into heat. In experi- 

 ments in the respiration calorimeter a very close agreement 

 is found between the calculated and observed heat or energy 

 liberations. This is illustrated by the results of one of the 

 Atwater and Rosa experiments. The figures are the daily 

 means from tests running through 4 days: 



Total energy of food, determined 3,678 Cal. 



Energy of urine and f eces 264 



Net energy '. . . . 3,414 



Energy of fat lost 488 



3,902 

 Energy stored as protein 38 



Total energy of material actually oxidized 3,864 



Heat actually measured 3,739 



125 



There is, therefore, a difference of only 125 large calories in 

 this test, which was one of the early ones with the new appa- 

 ratus. In later experiments described by Atwater and his col- 

 leagues much closer results have been reported, which shows 

 the general correctness of the method of calculation followed. 

 Effect of Work. To maintain the individual at work a 

 greater expenditure of energy is necessary, and the total en- 

 ergy of substances metabolized must be balanced by the heat 



