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. Narcotism, the craving for narcotic or stimulant drugs, and its subvariety, alcoholism, has been found most often among the thymocentrics. Any type of endocrine inferiority, interfering with success in life, may lead to the habit of drug addiction as one way out. But the blood and tissues of the thymocentric appear to become habituated to the narcotic stimulant more easily than the other types, and so to demand it with a physical imperative comparable to the food or sex urge. Among artists, philosophers and statesmen, on the other hand, actively productive and so contrasted with criminals and degenerates drug addiction has frequently been a mode of endocrine compensation. That is, the drug produced temporarily the effects of the internal secretion lacking or insufficient. Thus the effects of cocaine may be compared with the effects of thyroid. But while there is a normal mechanism for thyroid detoxication, the cocaine or heroin derivatives mark the tissues permanently with their scars and deform the personality. THE HYGIENE OF THE INTERNAL SECRETIONS