CHAPTER VII. 



THE BACTERIA WHICH CAUSE CONSUMPTION, OR 

 TUBERCULOSIS. 



MORE than one seventh of all the people 

 who die are carried off prematurely by 

 consumption, or tuberculosis. But it is only 

 within the present decade that we have had 

 any definite knowledge as to the cause of the 

 disease. For a great while physicians have 

 known a great deal about it. They have be- 

 come very expert in detecting its advent and 

 in tracing its course, and came long ago to 

 know but too well whither it tended. The 

 disease was usually regarded as hopeless, and 

 its treatment was entered into rather for hu- 

 manity's sake than in the expectation of in- 

 ducing a cure. To-day the aspect of affairs 

 has greatly altered. We know that tubercu- 

 losis is caused, and caused alone, by exceed- 

 ingly minute, rod-shaped bacteria, which, in 



79 



