EXPERIMENTS ON METABOLISM OF ENERGY. I19 
water vapor given off by the body—i. e., of the water va- 
-porized by its heat and carried out in the air current, due 
corrections being made for water condensed upon the absorb- 
ers; (3) the heat equivalent of the muscular work done. 
In the measurements of energy of income and outgo of the 
body the temperature of the interior of the chamber, generally 
about twenty degrees, is taken as the basis for computations of 
the heat removed or given off by food, drink, and excretory 
products in the chamber.* 
(1) The heat carried away by the water current includes 
(a) the heat given off from the skin by radiation and conduc- 
tion; (6) that brought out of the body in the feces and urine 
and given off in the cooling of these excretory products to the 
temperature of the chamber; (c) that brought out of the body 
in the air, carbon dioxid, and water excreted by the lungs and 
skin and given off in their cooling to the same temperature; 
(d) the latent heat of vaporization of so much of the water 
of c as is permanently condensed on the’ absorbers (mainly 
collected as drip water), and (e) the heat produced by the 
transformation of the external muscular work. ‘The heat of a, 
b, c, and e finds its way by radiation and conduction to the sur- 
face of the copper absorbers and passes with that of d into the 
water current, by which it is carried out of the chamber. 
(2) Although the air current enters and leaves the chamber 
at the same temperature, it carries out more heat than it brings 
in. The extra heat carried out is the latent heat of the water 
vapor added to the air of the chamber by the subject.f The 
amount of this heat is learned from the amount of water vapor 
and its latent heat of vaporization at the given temperature. 
(3) The external muscular work is measured and the heat 
equivalent calculated. Before leaving the chamber it is trans- 
formed into heat, which is carried away by the water current, 
as above stated. 
Energy given off in different ways as heat and as external 
muscular work.—The average amounts of energy given off by 
the body per day in the different ways are shown in Table 28. 
* U.S. Dept. Agr., Office of Experiment Stations, Bul. 69, p. 20. 
+ The differences in specific heat of the air due to loss of oxygen and gain of carbon 
dioxid are here assumed to be negligible. 
