216 THE INVISIBLE WOKLD 



Milk from tuberculous cows, or water tainted 

 with, germs, may cause the disease. 



Most of all, infection takes place by breathing 

 the air in which the germs float. The sputum of 

 the consumptive always contains millions upon' mil- 

 lions of germs. In his room, on street or sidewalk, 

 car or coach, the sputum dries and crumbles to 

 dust, By stir of brush, broom or wind, particles 

 of dust, with germs clinging to them, rise and float 

 in the air. The air is breathed into the lungs; in- 

 fection is the result. 



In all these, and in many other ways, the con- 

 tagion of tuberculosis is communicated from per- 

 son to person. The germs are scattered broadcast 

 over the world. Everybody is exposed to the dis- 

 ease. All consumptives mingle freely with all 

 other people; the exposure is therefore inevitably 

 universal. 



Is it any wonder, therefore, that one seventh of 

 all the people die with tuberculosis? Is not the 

 wonder, rather, that more do not die with it? In- 

 deed, that all do not have the disease? 



Why not? One reason, and one only, a wise 

 provision of Nature forbids. By Nature, the larger 

 portion of mankind, say six-sevenths, is not predis-* 

 posed to consumption. All individuals of this por- 

 tion are immune. They cannot have the disease. 

 But the other portion, say one-seventh of mankind, 

 is predisposed to, can take, does take, the disease, 

 and dies with it in vast numbers. 



Why this is so, why one portion of mankind is 



