268 THE INVISIBLE WOELD 



They all, except one, enter the body before pro- 

 ducing disease, by the air passages, digestive 

 tract, or wound. 



Once in the body, they all subsist on substances 

 in the blood or in the tissues. 



In their life processes they all generate poison, 

 forty-four kinds of poison forty-four kinds of 

 sickness and death. 



By the same means, too, each germ is known to 

 be the sole cause of a particular disease. 



First, the germ is always present in the disease. 



Second, the germ is isolated. 



Third, of the germ a pure culture is made. 



Fourth, a speck of this culture is used to inocu- 

 late some lower animal. 



Fifth, the animal has the disease. 



By these means the forty-four kinds of microbes 

 are known to be the causes of the forty-four kinds 

 of diseases. 



Of the 1,500,000,000 people on the earth, each 

 one is in danger, however slight, it is yet danger. 

 He knows not how soon he may be attacked by 

 some one of the foes, the next year, or the next 

 moment. 



" To be forewarned is to be forearmed." 



Such, Summed Up, Is the Great Fact. 



