The second function, or rather group of functions to be considered in
the study of metabolism is the generation of heat and energy. If the
reader will recall what was said in Lesson II, regarding the production
of heat by the process of oxidation, he can more clearly comprehend the
method by which heat is produced in the animal body. However, as heat
is only one form or expression of energy, these two subjects--heat and
energy--should be considered together.
[Sidenote: Heat and energy produced by oxidation]
The production of heat and energy in the body occurs almost entirely
through the oxidation of food. All three classes of foods, namely
proteids, carbohydrates, and fats can be oxidized to produce heat.
[Sidenote: Heat, a measure of energy]
Energy may be mechanical, chemical, electrical, or thermal. The
conservation of energy, which is one of the fundamental laws of science,
teaches that no energy can be lost, but can only be changed into other
forms. This being true, and because all energy can be changed into heat,
we use heat as a measure of energy.
[Sidenote: The "calory," a unit of heat]
The unit of heat, and consequently of energy, that is used by scientists
is the "calory," which is the amount of heat required to raise the
temperature of one thousand grams of water one degree on the centigrade
thermometer scale. The energy in food is measured in calories, as will
be learned from the explanation given in the lesson entitled "Vieno
System of Food Measurement."
[Sidenote: Liberation of energy through metabolism]
The Vieno is merely a unit especially convenient in measuring the energy
in food. In order that this energy may be drawn upon or liberated in
the body, it is necessary for the food to pass through the process of
metabolism, as heretofore described.