A successful campaign in the interest of public health must be based on something more than a knowledge of the mode of transmission of communicable disease. This, without doubt, is one of the foremost considerations in any program for the promotion of the public health, as it also is in relation to personal prophylaxis. But the problems of preventive medicine involve factors of widely different origin and significance, each of which must be evaluated and assigned a corresponding responsibility. Premature breakdown and premature death, for example, have been attributed to a diversity of causes, such as heredity, infections, poisons, mental strain, physical strain, mental inactivity, physical inactivity, accidents and improper diet. Obviously, each of these categories of alleged influences demands special and somewhat unlike consideration in any effort to control or modify the mortality of a group. As Chief Justice Taft has remarked, "while it is true that to the