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.