Thus, the growth of the brain is presided over by the adrenal cortex, the thyroid, the thymus and the pituitary. They determine the size of the brain, the number of its cells, the complexity of its convolutions and the speed of its chemistry, which means the speed of thought and memory and imagination. As its directorate, therefore, they may be entitled. The disturbance of one of them means the disturbance of all of them, and a consequent deleterious effect upon the brain. Now take the burning up of sugar in the organism, the great material source of energy, which is controlled by the pancreas, the adrenals and the liver, the thyroid and the pituitary. Together they form the directorate of sugar metabolism. But, as is evident from a glance at the membership of the growth directorate, and comparing it with the directorate of sugar metabolism, there are some members who are present on both boards. An infection, an illness, an ailment, an exaltation or intoxication of such members will produce reverberations in both directorates. A disturbance of sugar metabolism might then cause a disturbance of growth. The advantages and disadvantages are before us of having, in the glands of internal secretion, an interlocking directorate, rulers over all the varied and manifold activities of the organism.
Behind the body, and behind the mind is this board of governors. Indeed, from the administrative and legislative points of view, the body-mind may be said to be governed by the House of Glands. It is the invisible committee behind the throne. Upon the throne is what? Man, the most baffling of complexities. Man who is not a mind, but owns a mind—Man who is not a body, but possesses a body, just as he might have a motor car, a fortune or a calamity. Back of all his daily activities, behind the life of body-mind is the mysterious unique individuality, the Ego, the Psyche or the Soul. Lately, a competitor with these ancient and honorable terms has come upon the scene as the Subconscious. In that darkened No Man's Land is determined a man's destiny. The endocrine association stands out as at least the most important physical determinant of the states and processes of the subconscious.
ANTAGONISMS AND CO-OPERATIONS
As within a corporation there are factions and cliques, influences that always work together, and forces that are always pulling in opposite directions, so within the interlocking directorate of the ductless glands there are antagonisms and inhibitions, co-operations and compensations. One gland will assist the action of another's secretion with its own, or will in turn be stimulated to secrete by it. Another will throw out its secretion in order to neutralize the effects produced. Or its own activity will be depressed or completely inhibited by it. Thus the pituitary arouses the interstitial glands and vice versa, whereas the pancreas and the thyroid are mutually inhibitory. Indeed, whole systems of glands may work in unison, or be pitted against each other in certain situations, especially when the organism is subjected to conflicting impulses with the clash of opposing instincts, like fear and anger. In general there is reciprocity and team work among the internal secretions.
A certain minimum amount of each must be present if life is to continue along the normal lines. Whether there is to be an excess of any one secretion above this minimum, or a deficiency below it, decides the fate of the individual. If there is deficiency of one, the other members of the directorate attempt to make up for what has been lost, and to carry on its work by an extra effort, to substitute. Or, released from the discipline of the deficient member, or the necessity for antagonizing it, they may be released from its stimulus to secrete, and produce less of their own specific secretion. A general reaction all along the line will accompany overaction, oversecretion, of one gland. Due to consequent stimulations and depressions of other glands, some may be excited by the event to overwork—some to assist—others, to act as antidote for—the excess secretion, while still others, relieved of a burden, do not have to supply as much of their quota under the circumstances and so shut down, or limit their output.
It is important to get clearly in mind these subtle inter-reactions of the different ductless glands. They may be antagonistic in their end effects because of the opposed functions of the nerves or organs stimulated. There are inhibitions and restraints produced when a gland will send out its secretions to stop another gland secreting. There are compensations resulting when because of insufficiency of a gland, others will endeavour, by manufacturing more of their own secretion, to compensate for the loss. There are mutual co-operations, partnerships, when a gland will oversecrete to assist another, or in response to another which is also oversecreting. There are losses of balance, so that when one gland ceases secreting, another will simultaneously or soon after. Normal secretion, oversecretion or undersecretion are thus adjusted, but leave a train of after effects.
So with loss or insufficiency of the thyroid, there may be pituitary overgrowth, because the pituitary may act as vicar for the thyroid. The thyroid and thymus are antagonistic, for the thyroid hastens differentiation, puberty and the coming of sexual maturity, while the thymus delays and retards them and prolongs the period of childhood. The thyroid and the pancreas are antagonists, for when the thyroid has been excised, the pancreas appear no longer necessary to act as a break upon the mechanism of sugar liberation into the blood from the liver. The thyroid stimulates the interstitial glands, for menstruation and pregnancy are impossible with no thyroid or an insufficient thyroid. Removal of the pituitary makes the thymus shrink because the restraining influence of the latter is no longer needed. But there is an enlargement of the thyroid to compensate. In castrates there is an increase in the size and number of the cells of the anterior pituitary, again a compensation or substitution effect. The pituitary and the adrenal cortex are mutually assistant, alike in their influence upon the tone of the brain and sex cells.
THE KINETIC SYSTEM
So there are combinations of glands to assist or restrain others, or to control a body function, or to determine the domination or abeyance of an instinct. One such has been named the kinetic system because it comes into play in situations which demand prompt adaptation without hesitancy, and a consequent immediate transformation of static or stored energy into kinetic or active energy. According to this conception the brain, the adrenals, the liver, the thyroid and the muscles together constitute a machine very much like an automobile. The self-starter of the machine is the brain, with storage battery (composed of stored past memories) and ignition combined. The thing seen without, or the idea felt within, act as the initial sparks, while the adrenals, as the carburetors, permit the freer flow of fuel, sugar, from the liver. The thyroid works as the accelerator, the original impulse 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.