There is no other subject within the domain of medicine that appears to be attracting the attention of the profession at the present time to so great an extent as the prevention and treatment of tuberculosis. And certainly no other disease has greater claims on our attention, an account of its very general prevalence in all the countries of Europe and America, and the great mortality occasioned by it, being equal to one-eighth of the total mortality from all diseases.
To enable us effectually to devise and execute means for preventing or limiting the prevalence of any given disease we must know something of its causes, or, at least, of the conditions under which they become active as well as of the conditions under which they cease to act or are destroyed. Consequently, a correct and full knowledge of etiology contitutes the only legitimate basis for preventive medicine. It is