The Bacteria of Consumption 85 



But after a while, the poisons of the tubercle 

 bacilli destroy these new-formed tubercles as 

 well as the lung itself and then they often be- 

 come friable and break down. Thus cavities 

 of considerable size may form in the lungs. 

 Plate VIII. shows a series of such cavities. 



On the walls of these cavities the tubercle 

 bacilli often grow in enormous numbers and 

 as the cavities usually connect with the 

 bronchial tubes, the bacilli may be cast out 

 in the sputum. 



We know that tuberculosis is never caused 

 by any other thing than the tubercle bacillus, 

 and that even in persons predisposed by in- 

 heritance or otherwise to the disease it cannot 

 occur unless this particular germ gets into the 

 body from outside. The germ itself has rarely, 

 if ever, been shown to be directly inherited. 

 If, therefore, we could keep this particular 

 germ away from human beings, there would 

 be no more tuberculosis, no matter what 

 the inherent tendencies of the individual 

 might be. 



In fact, human beings in general are very 

 resistant to the incursions of the tubercle 



