(11) The need of ventilation in so far as the comfort of the person 
under experiment is affected by the proportions of carbon dioxid, 
and water in the air in the respiration chamber. 
(12) Finally, a large amount of time, thought, and labor has been 
devoted to the elaboration and testing of the apparatus and methods 
of experimenting-. Five years were thus used before the first actual 
experiments with men were made, and more or less attention is being 
constantly given to the same subject. 
GENERAL PLAN OF THE APPARATUS AND THE EXPERIMENTS. 
The description of the apparatus and the methods of manipulation 
of the experiments have been given with sufficient detail in the former 
publications already referred to. It is sufficient to say in this connec- 
tion that the essential features of the apparatus are a chamber large 
enough to permit a man to stand up and lie down at full length: appli- 
ances for measuring and analyzing a ventilating current of air; arrange- 
ments for passing food and drink into the chamber and removing the 
solid and liquid excreta, all of which were carefully weighed and 
sampled for analysis; and devices for determining the heat given off 
from the body of the man in the chamber, and. in work experiments. 
for determining the heat equivalent of the muscular work done. 
Measurements were made of income and outgo of both matter and 
energy in the man's body during the period of the experiment. The 
chemical analyses included determinations of the total quantities of 
the nitrogen, carbon, hydrogen, water, and mineral matter of food, 
drink, and respiratory and excretory products. In obtaining the 
income and outgo of energy, the potential energy of the food eaten 
and of the solid and liquid excreta was determined by means of the 
bomb calorimeter, and the kinetic energy given off by the subject 
was measured by the respiration calorimeter and accessory apparatus. 
TEST EXPERIMENTS. 
Before the respiration calorimeter can be used in such experiment- 
ing, its accuracy, both as a respiration apparatus and as a calorimeter, 
should be demonstrated. Two methods have been adopted for testing 
its accuracy; first, by generating known amounts of heat electrically, 
and. second, by burning known amounts of pure ethyl alcohol within the 
respiration chamber and measuring the heat and the chemical products 
of combustion. The mean of rive electrical tests of the apparatus, 
made previous to the experiments here reported, showed a variation 
between the heat actually measured and that generated so small as 
to be far within the limits of experimental error. The mean of nine 
experiments, in which known amounts of ethyl alcohol were burned 
within the chamber of the calorimeter and the carbon dioxid. water, 
