But personality and its reactions, normal and abnormal, are determined by the endocrines.  So we should find that particular infections run with special internal glandular predominances.  For the picture presented by an infection, temperature, rash, prostration, are the details of the general reaction of the organism in the face of a new situation, the presence of a powerful, destructive invader.  Information has accumulated that the invader is powerful and destructive, as well as selective, because of endocrine deficiency of one sort or another in the body it has attacked.  Work of a number of investigators has indicated that an individual’s susceptibility or its reverse, resistance, is intimately subjected to the derangements or harmonies of the endocrine system.

Comparison of the endocrine type and the disease assaulting has yielded an even more interesting principle.  Knowing the state of the internal secretion reservoirs enables us to predict the liability to certain of these infections of childhood.  Diphtheria has been found to occur most virulently among adrenal poor individuals.  Moreover, they are left poorer in adrenal afterwards.  It follows that they would be assisted by the feeding of adrenal.  Mumps is a sickness that sometimes permanently injures the gonads:  the testes or ovaries.  The thyroid dominant, whose system is rich in thyroid, will rarely suffer from any of the common diseases of children—­if at all, from measles.  Op the other hand, those who have every infection of the period, and who, as their mothers say, seem to get everything, are those whose system is thyroid poor.  Thyroid poverty is a splendid enticement to the universal microbe.  The thymocentric stands all diseases poorly.  The pituitary type is more liable to epidemic meningitis and infantile paralysis, typhoid and scarlet fever.

The public health officer of the future will be armed with a new weapon in his fight against the spread of an epidemic.  He will be able to classify the endocrine traits of the population exposed, and to advise a course of glandular feeding for the types specially liable.  The Schick test for diphtheria susceptibility is an illustration of one method of approach to the problem of the epidemiologist in settling who needs protection.  The endocrines will assist him in the great body of diseases for which no immunity test is at hand.  Should another influenza epidemic come along, for instance, the proper handling, from the endocrine standpoint, of the thymocentrics and the related adrenocentrics would help considerably in lowering the mortality.

Endocrine types have other tendencies, which when studied and controlled, will decimate the great assassins of middle age:  heart disease and kidney disease, with accompanying degenerations of the blood vessels and circulation.  The adrenocentric tends to get up a hyperacidity of the stomach and a high blood pressure, besides certain forms of diseases of the lungs.  The thyrocentric is predisposed to heart disease, as well as intestinal disturbances.  The pituitocentric is liable to periodic and cyclic upsets in his health.