52 DUST AND ITS DANGERS. 



more persistent protean catarrhs with which so 

 many persons otherwise healthy are burdened. 



Then again dust may produce much distress 

 when not inhaled, by irritating the eyes to such 

 a degree as to cause great discomfort, if not 

 positive disease. 



Smoke, which is a growing evil in many 

 cities, is a kind of dust which, though not so 

 obviously pernicious as some other forms, is 

 still capable of doing serious damage in the 

 long run to the delicate respiratory organs. 

 Improperly managed motor vehicles which 

 smoke, are responsible for injury to citizens 

 in this way and should be treated as nuisances 

 by health authorities. 



As to the bacteria about which our main in- 

 terest centres, there are unfortunately a few 

 species which, when they once find lodgement 

 in one place or another in the organs of 

 respiration, may grow and multiply, and suc- 

 cessfully resisting all the protective agencies of 

 the body, set up distinct, persistent and even 

 fatal disease. Those forms of bacteria which 

 can or in these regions commonly do this, are 

 insignificant in number in comparison with the 



