Heredity affects health through the inheritance of good physique and intelligence. Under the heading of social environment, nutrition is by far the greatest single influence on physical welfare, exceeding by a considerable margin parental care, housing, sanitation and other elements which depend fundamentally on wages. Occupation affects health in a great many direct and indirect ways. In any event, it is a particularly difficult assignment to dissociate the effects of these three factors one from the other. Nevertheless, Vernon feels it worth while to set up certain percentage relationships between these factors, tentatively at least, until further observation by him and others may suggest abandonment or further exploration of this method of evaluation. These, in substance, are a few of the author's reflections on a most interesting subject, which, at least in this country, receives far less consideration inmedical publications than it deserves. This book refers mainly to British conditions,