"It will be apparent to the casual thinker that many diseases and many causes of death are due to environing conditions for which he is in no way responsible. These range all the way from purely external occurrences to hereditary predispositions. They might be listed as follows: 1. Accidents... 2. Infections coming to a man from outside and not as the result of his own peculiar blood condition... 3. Diseases due to malnutrition, particularly when found in the young... 4. Heredity. There are, as you well know, certain forms of hereditary weaknesses..."