Now the concept of personality, as woven around a system of chemical reflexes, handed on from generation to generation, is bound to change all that, and to create a structure of positive eugenics.  It has been said that what radium is to chemistry, the internal secretions are to physiology.  Just as radium enlightens the chemist about the history of matter, and the integrations and disintegrations constituting the life of an element—­the internal secretions illuminate the history of the individual as part of the life of the race, and of its integrations and disintegrations.  Seeing the individual as a system of chemical substances interacting will assist enormously to predict the nature, character and constitution of his descendants, which is essentially what the eugenist is after.

The study of matings, the heart of the matter, will concern itself with the investigation and comparison of the kind of endocrine personalities that mate, the internal secretion predominances that cross, and the consequent endocrine personality of the offspring.  Data bearing upon physique and physiognomy, details of anatomy and function, mind and behaviour will so be co-ordinated as no eugenist has hitherto succeeded in doing.  Laws of endocrine inheritance will emerge that will bring the control of heredity within measurable distance.  Standards and norms of a new kind would be obtained.

A beginning of this study of endocrine inheritance, on the pathologic side, has been made.  Some of these have been along Mendelian lines.  Following up abnormal growth (making giants and dwarfs) and abnormal metabolism (goitre, diabetes, and so on), it has been stated that it would seem that abnormal growth is dominant in the male, and recessive in the female, while abnormal metabolism is dominant in the female and recessive in the male.  If an endocrine abnormality like a goitre, or cretinism, or a dwarf or giant appear in a family as a sign of endocrine instability, other members of that family will very likely show internal secretion abnormalities.

If one gland of internal secretion acts as the centre of the system and the others as satellites, we should be able to trace what happens to it in the different generations.  Does it maintain its supremacy?  Or will it be ousted by another member of the group?  The time will come when we shall thus be able to advise prospective parents of the consequences of procreation and to forecast the meaning for the race of a particular marriage.  Internal glandular analysis may become legally compulsory for those about to mate before the end of the present century.