106 DUST AND ITS DANGERS. 



nowadays about bacteria and germs and infec- 

 tion and the need of a more intelligent 

 cleanliness. 



It is not a mere fashion at whose dictates 

 the doctrine of cleanliness in person, food, and 

 air is being so widely and earnestly proclaimed 

 to-day. It is no fad of the hour which is to pass 

 and be forgotten. If our research into the 

 sources of widespread human ill does carry us 

 down into the realm of the invisible world we 

 bring from it such knowledge as is full of 

 significance and rich in the promise of human 

 weal, if we do but heed the lessons which are 

 already clear, precise, and not easily to be 

 mistaken. 



