THE STORY OF THE BACTERIA. 1 09 



serve at once as kitchen, dining-room, garbage 

 reservoirs, and bedchambers. But among 

 those more fortunately circumstanced, the con- 

 veyance of the diphtheria, and probably of 

 typhoid-fever germs, on uncleansed spoons, 

 dishes, etc., is of no infrequent occurrence. 



The Air as a Source of Bacterial Infection. 



We have seen that the only way the air 

 which we breathe can be actually infectious, that 

 is, can be the means of transmitting a bacte- 

 rial disease, is, under ordinary conditions, by 

 carrying as dust the dried but living disease- 

 producing germs from some infected individual 

 or animal along with other and less harmful 

 dust. Thus it is that our recently acquired 

 knowledge of bacteria and other minute or- 



o 



ganisms has brought a new significance into 

 the problems of ventilation. Foul air we still 

 know to be bad and capable of inducing seri- 

 ous forms of disease, but the specific and most 

 significant elements of positive danger reside 

 in the floating dust. 



The possibility of taking the bacteria of 

 tuberculosis and diphtheria into the mouth 



