It is needless to state before physicians that direct bacillary transmission of tuberculosis is possible. Tubercle bacilli have been found in the placenta of the tuberculous mother and in the new-born babe; but when we deal with the social aspect of tuberculosis we can consider the occurrence a negligible factor because of the relative rarity of direct tuberculous heredity.
Tuberculosis in childhood we have learned to ascribe mainly to a postnatal infection from a tuberculous parent, particularly the mother, and in a small percentage (about 10 per cent.) of the cases among artificially fed babies, to bovine tuberculosis. The predisposition to tuberculosis, which is surely and often inherited, comes from what may be called a physiologic poverty. A child of a tuberculous father or a tuberculous mother brings with it as a heritage a general weakness, its entire physical make-up having the imprint of diminished resistance. In other words, it