All these protean expressions of endocrine determination may now begin to be looked upon with the hopeful and optimistic attitude of him who understands cause and effect and can control. The advances made in the last ten years in the practical manipulation of the ductless glands from without, the introduction of glandular extracts by feeding or injection, and the modification of their structure and function by surgery, the X-ray and radium, and other procedures, enable us to regard more confidently the problems hitherto accepted as the insoluble and intricate handiwork of Fate. Fate may have woven the patterns of our being. But as we commence to probe the machinery and to examine the looms more carefully, we begin to understand why the wheels creak, and why there are seconds and odd lots in the product as well as the rare and precious firsts. Moreover, we are learning how to handle the machinery ourselves. The abdication of Fate can therefore be confidently expected in due time. However, we have yet to begin, and we can begin with prevention. The theory of Adler, that some organ inferiority is responsible for much unhappiness in life has received much advertisement in conjunction with the doctrines of the Freudians. It is a theory of little scope when applied to the eyes, ears, heart and so on because only a small minority of the cases are of that kind. But as we have seen, a deficiency of an internal secretion, an endocrine inferiority, reverberates throughout all the cells. Not only the mind, but all of the members of the organism must strain and co-operate to make up for the break in the balance. Endocrine inferiority is indeed the most frequent organic inferiority. And we may explain a number of mental types upon that basis. Thus the inferior gonado-centric, who has something wrong with his reproductive organs, will evolve in one of two directions. If his adrenal and thyroid are of poor quality, he will become the secluded introvert, shut off from the interests of normal life. He will enter the borderland of insanity if pituitary difficulties supervenes. If, on the contrary, the adrenal, thyroid and pituitary are present in a certain proportion, he will become the active, aggressive, never-resting, keen, and relentless fanatic reformer. A woman who is gonad deficient with a superior adrenal will suffer from virilism and specialize in the extreme tactics and mythology of the feminist movement. A number of life reactions are classifiable as the strivings of endocrine inferior individuals to overcome their sense of inferiority. The unconscious vegetative system and the system of consciousness are both modified by the weakness of a link in the glandular chain.