and liver, which are exhausted.
Exhaustion diminishes when the activity of the brain is diminished by
anesthetics, and cured when it is abolished by sleep.

If the adrenal gland may be called the Gland of Emergency energy, the
Kinetic System is entitled to the name of Council of Emergency Defense
for the organism. The Kinetic Drive is the name that has been given to
the whole system at work. It is one of the best examples we have of
inter-glandular co-operations and reactions in reply to the threat of
danger or the hint of pleasure.

THE CHECK AND DRIVE SYSTEM

Another instance of the complexity of these inter-glandular reactions
is furnished by the thyroid and the adrenals. The thyroid and the
adrenals are mutually stimulating--when the thyroid oversecretes, the
adrenal dittos, and vice versa. Yet they have directly opposed effects
upon the economy--because they act upon antagonistic portions of
the involuntary or vegetative nervous system, the system which is
independent of the will. Before proceeding further, it is worth while
sketching this division of the nervous system.

In the construction of a motor car from the point of view of absolute
control of it at every moment, the first thought of the mechanic is an
adequate _brake_ and an efficient _regulator_ of speed, instruments
antagonistic, but necessary to work simultaneously or alternately.
The involuntary or vegetative nervous system is built upon the same
principle. It supplies every organ in the body beyond the control of
the will (that is to say, the brain) with two sets of filaments which
have opposing functions. One group of filaments in general increases
or activates the function of the organ to which it is distributed. The
other group of filaments, when tingling, inhibits or prohibits that
function. They are like the two buttons on the wall which regulate
the supply of electricity to incandescent bulbs, one switching on the
current, the other switching it off. It has been agreed to call the
stimulative or activating portion the autonomic or drive system. To
its antagonist has been left the older name of the sympathetic or
check system. It is because they do not both act upon these two
components of the vegetative nervous system, but only upon one, that
the thyroid and adrenal though in themselves complementary, come to
exert opposite effects. For the internal secretion of the thyroid has
a selective affinity for the autonomic or activating system, whi