The Respiration Calorimeter.
between. It is in this closed inner chamber, lighted by plate
glass windows and supplied with a constant current of pure
air, that the animal is placed during the experiment, being
admitted by large doors at one end. The temperature of the
chamber can be regulated to the hundredth of a degree, food
is regularly given through special doors, and the animal
stands or lies down at will.
The object of the apparatus is to study the food as a
source of energy, or, in other words, as the fuel of the body.
Food is burned in the body somewhat as coal is burned in a
locomotive and gives much the same final results, viz., heat
and motion. A bushel of corn or a bale of hay if burned in
a furnace gives off a certain definite amount of heat and
energy. The aim of the experiments to be undertaken with
the respiration calorimeter is to find out what proportion
of this energy can be utilized by the animal io produce meat
or milk or work, and how much is simply used up in heating
the surrounding air. A comparison of corn and hay, for
example in this respect, will show which one contains the
greater store of energy in available form. Similarly a com
parison may be made of the ability of different animals to
utilize the same food, or of the influence of various external
conditions, such as temperature, water supply, light, excite
ment, etc.
The comparisons are made much as we might make them
with a locomotive. Knowing the energy contained in the
coal, an analysis of the waste products, including the gases
from the stack, and a determination of the heat given off,
would furnish the elements necessary for the comparison.
In the case of the animal, the visible excreta can be readily
collected and analyzed by proper appliances. The flue gases
are represented by the breath of the animal, the gases of
which are carried out of the chamber in the current of air.
The air current is maintained by an ingenious piece of appa
ratus specially designed and built for the purpose by Mr.