CHAPTER IX 



TUBERCULOSIS. LEPROSY 



Tuberculosis is the most widespread disease 

 known. In the United States it was estimated that 

 one ninth of all deaths which occurred in 1900 were 

 due to tuberculosis, and that the cost to the country 

 reached nearly to $200,000,000. 



Historical. — During 1870-1880 different investiga- 

 tors proved that tuberculosis was an infective disease 

 but did not discover the organism which caused it. 



"The announcement of the discovery of the tubercle 

 bacillus was made by Koch in March, 1882, and a full 

 account of his researches appeared in 1884 {Mitth. a. d. K. 

 Gsndhtsamte., Berlin). Koch's work on this subject 

 will remain as a classical masterpiece of bacteriological 

 research, both on account of the great difficulties which he 

 successfully overcame and the completeness with which 

 he demonstrated the relations of the organism to the dis- 

 ease. The two chief difficulties were, first, the demon- 

 stration of the bacilli in the tissues, and, secondly, the 

 cultivation of the organism outside the body. For, 

 with regard to the first, the tubercle bacillus cannot be 



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