The cultivation of a popular sanitary conscience is an object of supreme importance to the well-being of any community, and the connection between tuberculosis and bad general sanitary conditions can be utilised to the full extent in stimulating this conscience. There are few sanitary improvements that do not in some measure tend to hinder the spread of tuberculosis. Tuberculosis can be extirpated similarly, if similarly the slow effect of only gradually improving sanitary circumstances be supplemented by special measures having a more rapid and specific effect on the disease. Variations of virulence in the specific micro-organisms are known to have occurred with some infectious diseases. The evidence of the transmission of susceptibility has not been sufficient to show that this transmission occurs so frequently as to be a predominant factor in the transmission of the disease. The suggestion is that the long stream of emigration from Ireland has left behind it a physically inferior population of excessive susceptibility to phthisis.