64 DUST AND ITS DANGERS. 



erty and want and crime which among the 

 poor are wont to cluster about and to follow 

 such premature and lingering death ? Probably 

 the actual suffering and distress caused by all 

 other diseases put together is far less than 

 that which in one way or another is associated 

 with consumption. 



Now where do all these people get this most 

 widespread disease ? How do they become 

 infected ? Where do the living bacilli of this 

 particular species come from which get into 

 their bodies ? They do not grow at the tem- 

 perature of the air out-of-doors. There are no 

 lurking-places for them in nature apart from 

 those men or animals who have the disease. 

 Plant them artificially with other common bac- 

 teria in tubes in the laboratory and they die ; 

 they succumb in the struggle for existence 

 with the harmless species of the earth and 

 water and air. 



In a certain number of cases they no doubt 

 are taken in with the food, and inasmuch as 

 tuberculosis of cattle is a very common disease 

 all about us, there is every reason for believing 

 that the infection often enough occurs through 



