A NI3IA L HE. IT. 177 



1.8 per cent, is lost in the urine and feces 47,500 calories. 



3.5 " " " expired air 84,500 



7.2 " ■" " -evaporation of water from the lungs 182,120 " 



14.5 " " " " " " skin. 364,120 



73.0 " " " radiation and conduction from skiu 1, Till, 820 " 



2,500,000 calories. 



Therefore, about 87.5 per cent, is lost by the skin, 10.7 per cent, by the lungs, 

 and 1.8 per cent, in the urine and feces. 



O. Heat-production and Heat-dissipation. 



Calorimetry. — The intensity of heat of any substance is measured by means 

 of a thermometer or thermopile ; the quantity of heat present is estimated by 

 the weight, the specific heat, and the mean temperature of the body ; the quan- 

 tity of heat dissipated is measured by the calorimeter ; and the quantity of 

 heat produced is determined by the quantity dissipated plus any addition of 

 heat to that of the body or minus any that is lost (p. 481). The calorie, or heat 

 unit, is the quantity of heat that is necessary to raise the temperature of one 

 gram of water 1° C. ; the mechanical unit, or grammeter, is the quantity of 

 energy required to raise one gram a height of one meter, 424.5 grammeters 

 being equal to 1 calorie; a kilocalorie or kilogramdegree is equal to 1000 

 calories, and a kilogram meter to 1000 grammeters. By specific heat is meant 

 the quantity of heat required to raise the temperature of any substance 1° C, 

 this quantity varying considerably for different substances. It" water be 

 taken as 1, as a standard of comparison, the specific heat of the animal body 

 may be regarded as being about 0.8 ; in other words, 0.8 of the quantity of 

 heat will be required to heat the animal body as to heat the same weight of 

 water. Knowing the weight, specific heat, and temperature of any substance 

 the total quantity of heat stored in it at a given temperature, compared with 

 the same body at 0° C. may be readily calculated. Thus, if the animal 

 experimented upon weigh 20 kilos, its specific heat be 0.8, and its temperature 

 be 39°, the total quantity of heat stored would be 20 X 0.8 X 39° = 62.4 kilo- 

 gramdegrees. In calorimetric work the total heat in the organism is seldom 

 considered, but the specific heat of the organism is of importance in determin- 

 ing the quantity of heat involved in a change of the animal's temperature. For 

 instance, should the animal weigh 20 kilograms and its temperature be increased 

 or decreased 0.2°, the quantity of heat added to or taken from the heat of the 

 body, as the case may be, would be 20X0.8X0.2=3.20 kilograradegrees. 

 These calculations are of fundamental importance in studying heat-production 

 and heat-dissipation. 



In making estimates of the dissipation of heat no regard is paid usually to 

 the quantity lost in the urine and feces, because the error involved is so slight, 

 but the quantities imparted to the air, both in wanning the inspired air and in 

 evaporating water from the lungs and skin, represent important percentages. 



Calorimetry is spoken of as direct and indirect. The former method is 

 the direct determination of the amount of heat produced and dissipated ; the 



