572 



THE ANIMAL BODY AS A MACHINE 



from the nitrogen in the urine and in the feces. The carbon which 

 would be derived from this quantity of protein was deducted from the 

 total carbon output and the difference yielded the total non-protein 

 carbon, or carbon derived from carbohydrates and fat. The carbo- 

 hydrates in the food were measured and the corresponding quantity 

 of carbon deducted from the total non-protein carbon. The difference 

 represented carbon derived from the fat. In this way the quantities 

 of each of the three classes of foodstuffs consumed were estimated and 



FIG. 48. Schematic diagram of the Atwater-Rosa-Benedict respiration-calorimeter. 

 02, oxygen introduced as consumed by subject; 3, H2SQ4 to catch moisture given off by 

 soda-lime; 2, soda-lime to remove COz', 1, H2SO4 to remove moisture given off by subject; 

 Bl, blower to keep air in circulation; V, vacuum jacket; C, tank for weighing water 

 which has passed through calorimeter each hour; W, thermometer for measuring tem- 

 perature of wall; Ai, thermometer for measuring temperature of the air; R, rectal ther- 

 mometer for measuring temperature of subject. (After Lusk.) 



the energy which their combustion could yield was computed in the 

 manner indicated above and compared with the actual heat-evolution 

 of the subject. The results of forty days' experimentation with three 

 different subjects yielded the following averages: 



Calculated daily output . . . . . . ,/,., . ' . . 2717 calories 



Observed daily output 2723 " 



Difference, 0.2 per cent. 



A further refinement of technic consisted in the simultaneous esti- 

 mation of the carbon-dioxide output and the oxygen intake, from 



