DUST AND ITS DANGERS. 



I purpose then to show the difference of 

 conditions which prevail, in-doors and out, and 

 the significance of these conditions in the 

 problems of ventilation and cleanliness. I 

 shall then give the results of a series of studies 

 of the atmospheric micro-organisms in various 

 places, and consider the relationship of these 

 aerial germs to some common forms of disease. 

 Finally, I shall suggest some of the measures 

 which must be adopted, both by the public au- 

 thorities and private persons, if both outof- 

 doors and in-doors we are to have the privi- 

 lege of breathing clean and wholesome air. I 

 shall not, except incidentally, touch upon the 

 ordinary problems of ventilation or the numer- 

 ous ways in which by the accumulation of the 

 products of respiration and exhalation the air 

 of inhabited rooms may become an active 

 source of discomfort and ill-health, because the 

 means by which these evils may be avoided are 

 well known and are fully explained under the 

 heading of ventilation in text-books and treatises 

 on hygiene. 



