Country Air 61 



of streets, even though it increases the number of germs 

 in the road dust, is ngne the less valuable from the 

 hygienic standpoint. He evidently refers to the reduc- 

 tion in the amount of dust in the air caused by sprinkling, 

 whereby the number of pathogenic germs carried by 

 the wind is very materially lessened. The great value 

 of sprinkling is that it keeps the germs in the road dust 

 from being blown about by the wind. 



Bacteria in the air of the country. — Comparing the 

 number of bacteria in the air of the city and country, 

 we find, according to the examinations of Miquel, very 

 considerable differences. The average for his analyses 

 showed 300 bacteria per cubic meter of air taken outside 

 of the city of Paris, and 5,445 bacteria per cubic meter 

 of air taken within the city. Similar results were secured 

 elsewhere, thus confirming the conclusions reached by 

 Miquel. In the country, the number of bacteria in the 

 air is affected, among other things, by the presence or 

 absence of large forests. It has been demonstrated that 

 the latter may act as filters and hold back a portion of 

 the bacteria brought to them by the wind. This seems 

 to account for the fact that the air within forests is 

 poorer in bacteria than the air on their outskirts. 



Like the air of the forests, the air over the sea is also 

 poor in bacteria. The greatest number of bacteria was 

 found in sea-air taken in the vicinity of land. With the 

 increasing distance from the coast, the number of bac- 

 teria diminished until there was less than one germ per 

 cubic meter of air. Even poorer in germs than sea-air 

 was that from the polar regions, where but few could l^e 

 detected by repeated examinations. 



