38 
BACTERIA IN THE AIR— 
1. Number : 
Sewer air. 
Expired air. 
Sea air. 
City air. 
Country air. 
Air in houses, hospitals, etc. — 
Relation to the sun. 
Relation to habitation. 
Relation to winds and traffic. 
Relation to altitude. 
Pasteur’s method. 
Miquel’s method. 
Aeroscopes. 
Frankland’s method. 
Petri’s method. 
Hesse’s method. 
Straus’ method. 
« 
2. Varieties. 
3. Estimation of ammonia in the air. 
4. Estimation of carbon dioxid in the air 
