2. In the course of evolution, variations occurred in all three components of the apparatus, the viscera, the nerves, and the endocrines. Now variations in the viscera and the nerves are essentially grossly physical and quantitative. That is, there may be a bigger stomach or a smaller stomach, larger nerve fibres or smaller. And as Life always has worked with a large margin of safety, and always played for safety first as regards quantity, these variations have not become of much significance for the history and destiny of the animal.
But variations among the endocrines made a tremendous difference. To have very much thyroid and very little pituitary, much adrenal and not enough parathyroid meant a great deal to the Organism as a whole, as well as to the vegetative apparatus. For states of tension and relaxation, activity and inactivity in the nerves and viscera would be determined by these variations in the ratio between the variants. The vegetative apparatus in its virginity, say in the new-born infant, may be said to have its development primarily determined by the reaction potentials of the endocrine part of it, that is the latent power of each gland to secrete at a minimum or a maximum, and the balance between them.
EDUCATION OF THE VEGETATIVE SYSTEM
3. Training or education involves, beside other effects, a training of the endocrines, and hence of the entire vegetative apparatus, to respond in a particular way to a particular stimulus. Experience is like the introduction of new push-buttons, levers, and wheels into the mechanism. All learning which calls out or arrests the functioning of an instinct, must, from what we have learned of the chemical dynamics of instincts as reactions between hormones, nerves and viscera, affect the vegetative system. When there is a conflict between two or more instincts, between pressures of energy flowing in different directions, there may be compromise and normality, or a grinding of the gears and abnormality.
Where does the brain come in, in all this? As the servant of the vegetative apparatus. To call it the master tissue is manifestly absurd, when it can only be the diplomatic constitutional monarch of the system. It can, in fact, act only as the great central station for associative memory, as only one of the factors implicated in education.
The most powerful educative agents of the vegetative apparatus of a human being are the other humans around him. And they comprise the most powerful of the external effectors of education, for better, for worse. The training and education of the endocrine-vegetative system is the basis of all social rules (Habit, Custom, Convention, Law, Conscience). An unresolved discord, a continued conflict among the parts of the vegetative system, in spite of such education, is the foundation of the unhappiness of the acute or chronic misfits and maladjusted, the neurotic and the psychotic.
THE PHYSICAL BASIS OF THE UNCONSCIOUS
4. Another vastly important law that governs the content of the conscious and the unconscious, and resultant behaviour is the fact that the nerves and nerve cells of the vegetative apparatus, the nerves leading to the viscera and the endocrine glands, like the solar plexus, are affected by stimuli of lower value than those which arouse the brain cells. In the metaphorical language of the old psychology, the threshold value, that is the strength or loudness of stimulus sufficient to make itself felt or heard, is less for the vegetative apparatus than for the brain. So we begin to glimpse why an emotion seems to be experienced before the visceral changes that really preceded it, but pressed their way into consciousness later. This gives us a clue to the unconscious as the more sensitive and deeper part of the mind.
More than that, it supplies us with a physical basis for the unconscious which will explain much of the observed laws of its workings. It provides a reason for the apparent swiftness, spontaneity, and unreasonableness of what is called intuition. And it may show us a source for a good deal of the material of dreams and dream states.
We have said that we think and we remember, not alone with the brain, but with the muscles, the viscera and the endocrines. So do we forget not alone with the brain, but with the muscles, the viscera, the endocrines and their nerves. The utmost importance of muscle attitudes in remembering has been established in the experimental laboratory.