The chemistry of the soul! Magnificent phrase! It's a long, long way to that goal. The exact formula is as yet far beyond our reach. But we have started upon the long journey and we shall get there. Then will Man truly become the experimental animal of the future, experimenting not only with the external conditions of his life, but with the constituents of his very nature and soul. The chemical conditions of his being, including the internal secretions, are the steps of the ladder by which he will climb to those dizzy heights where he will stretch out his hands and find himself a God. Modern knowledge of these chemical substances, circulating in the blood, and affecting every cell of the body, dates back scarce half a century. But already the paths blazed by the pioneers have led to the exploration of great countries. The thyroid gland, the pituitary gland, the adrenal glands, the thymus, the pineal, the sex glands, have yielded secrets. And certain great postulates have been established. The life of every individual, normal or abnormal, his physical appearance, and his psychic traits, are dominated largely by his internal secretions. All normal as well as abnormal individuals are classifiable according to the internal secretions which rule in their make-up. Individuals, families, nations and races show definite internal secretion traits, which stamp them with the quality of difference. The internal secretion formula of an individual may, in the future, constitute his measurement which will place him accurately in the social system. "More and more we are forced to realize that the general form and external appearance of the human body depends, to a large extent, upon the functioning, during the early developmental period, of the endocrine glands. Our stature, the kinds of faces we have, the length of our arms and legs, the shape of the pelvis, the color and consistency of the integument, the quantity and regional location of our subcutaneous fat, the amount and distribution of hair on our bodies, the tonicity of our muscles, the sound of the voice, and the size of the larynx, the emotions to which our exterior gives expression. All are to a certain extent conditioned by the productivity of our glands of internal secretion." (Llewellys F. Barker, Johns Hopkins University, 1st President of Association for Study of Internal Secretions.)