The diarrhceal diseases of infancy are not as a rule properly to be regarded as com municable, but their prevalence has been greatly restricted through the work of health authori ties in the sanitary control of milk and, to a less extent, of the water-supply. The reduc tion during recent years in the death-rate from diarrhceal diseases of children under two, which has taken place almost everywhere in this coun try, is almost phenomenal, and indirectly the reduced prevalence of these diseases has ma terially decreased others brought on by them diseases of malnutrition, such as rickets, etc. The results which have thus been accomplished have been due almost entirely to increased medi cal knowledge and its intelligent application to preventive medicine.
Preventive medicine, however, in the truest, broadest and best sense, includes not only this work in the general application of medical knowledge to restricting the prevalence of the infectious diseases in the community, but also the application of medical knowledge to the protection of the individual from disease of all kinds at every stage in life from birth to old age, and it is this individual prophylaxis which has received the least attention either from the medical profession or from the people. Here is a very large field for intelligence work. A moment's consideration shows at once the impossibility of formulating general rules or of applying the same rules to all individuals, for it is a matter of common observation that individuals differ widely in their physical and mental characteristics, susceptibilities and tendencies. The occurrence in different families of certain similar types of disease in successive generations is a matter of general observation, and the influences which are injurious at one period in life may be not only not harmful hut beneficial at another. • It is most unfortu nate, from this point of view at least, that the family physician of former times is so erally disappearing. The ideal family physician knew thoroughly the family histories of his patients, their tendencies, susceptibilities, weak nesses; he watched every stage in the life of the child from birth; he knew where to re strain, where to encourage and what to pro hibit, where dangers to the physical well-being lay and how to advise them for self-protection.
In earlier days when the knowledge of disease was less extensive than at present, it was not within the power of the physician to advise as wisely as at present. It is well known now that disease as such is never inherited. It is too much the custom to think of disease as a definite entity, whereas it is really only an ab normal process. It is not possible to see or examine disease, as it has no existence as such, but in some instances the causes of disease may be studied, as is the case in the infectious dis eases due to known micro-organisms. In these may be investigated the micro-organisms caus ing the disease and the changes in the organ isms produced by the germs; so also may be studied the abnormal manifestations of life which these changes produce, those manifesta tions, which are called the symptoms of disease. The so-called inherited diseases which are of an infectious nature are simply instances of infection during intrauterine life, as tubercu losis and syphilis. The diseases of metabolism, such as gout, diabetes, adiposity, etc,, are not in stances of inherited disease, when they occur in different generations in the same family, as is frequently the case, but are the result of the transmission from parent to children of func tionally inefficient organs, which break down under the demands laid upon them.
Among the more recent additions to general prophylaxis are the movements now actively go ing forward to prevent mental diseases. This whole movement of mental hygiene is one of the most important of modern times. While it has been recognized for years that a healthy mind can exist only in a healthy body, it is being more and more emphasized that there can be no healthy body without a sound mind.
An absolutely efficient prophylaxis applied to the individual would permit the conduct of a physiological life from birth to its termination in a physiological death, occurring when the vital resistance with which the individual was endowed at birth was exhausted. With advanc ing medical knowledge and a higher civilization there should be a closer approximation to this condition in a larger and larger percentage of the population and a material prolongation of the mean lifetime.