THE CONQUEST OF DISEASE 



with the view of producing an antitoxin 

 against tuberculosis. The outlook is most 

 hopeful. The study of immunity in other 

 infective diseases leads to the hope that means 

 for producing immunity against tuberculosis 

 will come out of the researches which are now 

 being carried on in that direction. Further 

 knowledge of the toxins of this disease is con- 

 stantly being secured ; and there are abundant 

 reasons for the belief that prophylactic and 

 therapeutic measures, surpassing in import- 

 ance those now in the possession of man, will 

 soon be discovered. 



Since the tubercle bacillus was discovered 

 and it became known that the fight is against a 

 specific microorganism instead of some vague 

 constitutional weakness or hereditary suscep- 

 tibility, the mortality of the disease has steadily 

 declined. In 1886, 88,000 persons died in Ger- 

 many of tuberculosis : that is 31 per 10,000. In 

 1906, 64,000 died: that is about 17 per 10,000. 

 The same conditions prevailed in most other 

 countries. This is one of the reasons why the 

 span of human life has increased six years dur- 

 ing the past twenty years. Natural selection 

 and the laws of immunity also, perhaps, are op- 

 erating to reduce the mortality in this disease. 



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