396 GENERAL NUTRITION 



gram of water one degree C. is called a small calorie. One kilo- 

 degree = 1000 gram-degrees. 



One pound degree = 0.252 kilo-degree C. One kilo-degree C. = 

 3.96 (nearly 4) pound-degrees. A kilogrammeter represents the force 

 required to raise a weight of one kilogram one meter. One foot-pound 

 = 0.138 kilogrammeter. One kilogrammeter = 7.24 foot-pounds. One 

 pound-degree = 772 foot-pounds. One pound-degree = 1 06.6 kilogram- 

 meters. One kilo-degree C. = 422.25 kilogrammeters. One kilo-degree 

 C. = 3057 foot-pounds. 



Two methods have been employed in arriving at estimates of the 

 actual quantity of heat produced by the body in a definite time : 



1. The direct method consists in placing an animal in a calorimeter 

 and measuring the heat produced, making the necessary corrections. 

 This has repeatedly been done, but the results obtained have been 

 variable and not entirely satisfactory. An important element of inac- 

 curacy in direct observations one, indeed, which it seems impossible 

 to correct absolutely is due to the great variations in heat-produc- 

 tion with digestion, conditions of muscular repose or exercise, external 

 temperature etc. Another source of error is the difficulty in estimating 

 the heat lost by the body and not actually produced during the time of 

 the observation. 



2. The indirect method consists in estimating the heat represented 

 by oxidation, calculated from the quantity of oxygen consumed in the 

 processes that result in the production and discharge of carbon dioxide, 

 water, urea etc. These estimates have been compared with the calcu- 

 lated heat-value of the food consumed, and the results very nearly cor- 

 respond. 



According to the estimates of Helmholtz, Ranke and others, by the 

 indirect method, the heat-production is equal to about 2.5 heat-units per 

 hour per pound-weight of the body (1.39 kilo-degree C. per kilogram). 

 In a man weighing 180.4 pounds (82 kilograms) the heat-production in 

 twenty-four hours (Helmholtz) was 10,818 heat-units (2732 kilo-degrees 

 C.). According to this estimate, a man weighing 140 pounds (63.5 

 kilograms) would produce 8400 heat-units (2118 kilo-degrees C.) in 

 twenty-four hours. This would be equal to 6,484,800 foot-pounds, or 

 about 894,500 kilogrammeters. 



A study of this subject and of the details of observations both direct 

 and indirect has made it evident that the experimental difficulties 

 and the unavoidable elements of inaccuracy are greater in the direct 

 than in the indirect method. In comparing the estimates of heat actu- 

 ally produced with the heat- value of food which, of course, is the 

 ultimate source of heat and force in the body the correspondence is 



