finally landing upon muscles keyed up and supplied with food to meet the situation, be it that of removing a poison, removing an aggressor (attack) or removing the individual himself (running away).  When one is exhausted by exertion and emotion, injury, intoxication or infection, it is these members of the kinetic system, the brain, the adrenals, thyroid 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, while that of the adrenals has a selective affinity for the sympathetic or inhibiting system.