PREVENTIVE MEDICINE. Generally the term 'preventive medicine' has been re garded as almost synonymous with public hygiene and its application has been confined to the operations of the sanitary authorities in the prevention of the infectious and com municable diseases. These operations have not in the past included even all of the more im portant communicable diseases, although the list in recent years has been considerably ex. tended- Formerly cholera, plague, yellow fever, typhus fever, epidemic dysentery, small pox, scarlet fever, diphtheria and typhoid fever comprised all of the diseases which came specifically under the supervision of the public health authorities. Recently this list has been considerably increased by some sani tary boards. Many of the diseases referred to — for example, cholera, plague, yellow fever, epidemic dysentery—have practically passed from the supervision of the authorities, at least in the temperate zones, because either they no longer occur at all in these regions or only occasionally a case or a (group of cases appears and calls for specific action and super vision. The eradication of these epidemic diseases may be regarded as the greatest tri umph of preventive medicine. It will of course be noted that public hygiene or preventive medicine, in this restricted sense, taken little or no cognizance as yet of many exceed ingly important communicable diseases, such as syphilis, gonorrhoea, puerperal fever and, generally speaking, even of tuberculosis.
Preventive medicine in the proper sense has a very much broader scope than that indicated and may be defined as the sum of all medical knowledge applicable to the prevention of dis ease — of all disease in the broadest sense and not simply of the communicable diseases. It presupposes the widest knowledge of medicine and has its essential foundation in our knowl edge of the anatomy and causation of disease. Preventive medicine comprises, there fore, the prophylaxis of disease; it is general, comprising those measures which are applicable to the prevention of disease in the community (including especially the communicable dis eases), and it is individual, as applied to the prevention of disease of all kinds in the in dividual members of the community. General prophylaxis refers to what are spoken of as preventable diseases and these in the broad sense may be regarded as all of the infectious diseases which are communicable. Individual prophylaxis has, a still wider scope and in cludes the whole sum of medical knowledge as applied to the prevention of diseases (of all varieties) and the prolongation of life. Gen eral prophylaxis and individual prophylaxis do not always run along wholly parallel lines; for what is best for the individual is not neces sarily best for the community. Preventive
medicine is an applied science and includes all purely medical knowledge applicable to the at tainment of its aim. In securing its aim pre ventive medicine necessarily improves the gen eral physical well-being of the individual and thus life is rendered not only longer, but happier.
General prophylaxis attains its purposes in different ways. Through the establishment of sea quarantine it attempts to exclude infectious diseases which are endemic. These are spoken of as "quarantinable diseases' and they of course must differ with locality, depending upon what communicable diseases are endemic in a locality. In the United States, plague, cholera, typhus fever, yellow fever and leprosy are the diseases which the authorities especially attempt to exclude from the country. Scarlet fever, .measles, diphtheria and smallpox, being endemic, are not held at quarantine, but are referred to isolation hospitals for supervision until their termination. During recent years the quarantinable diseases have been almost completely excluded from this country. Oc casionally a case has been admitted at some point and a group of cases or a localized epidemic has followed; but in almost all in stances the outbreaks have been of a restricted and local character. It does not seem probable that in North America there will ever again be any serious danger of the prevalence of cholera, plague, typhus fever or leprosy. In dealing with the other communicable diseases specific methods have been devised, depending upon the nature of the disease and the method of its transmission. In some instances the at tempt is made to destroy the cause or prevent its entrance into the body; in other instances, to render the individual insusceptible to the cause and at the same time protect him from exposure to infection. For example, the cause of smallpox not being known, it is vain to attempt to destroy it in the individual; but as vaccination renders a person insusceptible to smallpox, it proves an absolutely efficient means for preventing the prevalence of this disease. In cities and countries where vaccination and revaccination are enforced smallpox rapidly disappears, and even when cases- are introduced from without, the disease does not extend. Thus in Prussia, where there is compulsory vaccination in infancy and revaccination at different intervals later in life, smallpox prac tically does not exist. In different portions of the United States the prevalence of small pox in epidemic form is determined in each instance by the thoroughness with which differ ent communities have been vaccinated. In the recent Great War less than a dozen deaths from smallpox took place in an army of 4,000,000 men.