To become adapted to their environment animals are transformers of energy.
This adaptation to environment is made by means of a system of organs
evolved for the purpose of converting potential energy into heat
and motion. The principal organs and tissues of this system are
the brain, the adrenals, the thyroid, the muscles, and the liver.
Each is a vital link, each plays its particular role, and one cannot
compensate for the other. A change in any link of the kinetic
chain modifies proportionately the entire kinetic system which is
no stronger than its weakest link.
In this conception we find a possible explanation of many diseases
one which may point the way to new and more effective therapeutic
measures than those now at our command.