The study of the glands is in its infancy. Throughout the literature on this subject, one finds statements to the effect that little is known, and that the inner essence - technically called "hormones" - of any particular glandular secretion has not yet been discovered, and that mystery veils the subject. It is true that the secretions of certain glands have been discovered, and that even in common parlance one hears of the thyroid gland and of the administration of thyroid extract in certain cases, but the secretions of most glands are unknown or have only partly been isolated.

In considering the endocrine system, it is not my intention to describe it in its ordinary physiological terms and effects, such as its relation to the growth of the body, to the hair, heart, blood and organs of generation. All this can be gathered out of any medical book, even those published in the last century. Rather is it my intention to ascertain what advanced and modern investigators, medical men and psychologists, infer from a study of the glands, and what they judge their effects to be on human behavior, and to check the claims, so often made, that the mysterious internal secretions are responsible for man's actions, emotions and mentality - in short, for the man himself. Understand the glands, they say, and behold the man.

In considering glands in this sense, I shall quote largely from the available books, not merely because one is then more likely to speak as having authority, but also because one thus reflects the given view more freshly and vividly. A partial bibliography will be found at the close of this book. [32]

These books, and the trained investigators as a whole, use a terminology that staggers the general reader. The secretion of the thyroid gland, for example, has been labeled as "tri-iodo-tri-hydro-exygindole-propionic acid!" As far as possible, I shall avoid such playful expressions.

Before considering the glands themselves, it is well to decide what we understand by "psychology." In the West at least, it has abandoned its derivative meaning, already given, of the logos or law, of the psyche or soul. A recent and clear definition is given by Dr. Leary:

"The science of human behavior in the largest sense of the word behavior, the sense which includes all that human beings do, all that human beings have. In this sense of behavior it is the behavior of the whole, integrated personality which is under investigation.

"Psychology deals with the organism as a whole, as an integrated and orientated individual in contact with other individuals in a complex external environment, partly physical and partly social, in short, as a personality.