BACTERIA IX THE AIR. 625 



ADDITIONAL NOTES UPON BACTERIA IN THE AIR. 



Ruete and Enoch (1895) have examined the air of closed schoolrooms 

 with the following results. Eighteen different species were obtained, only 

 one of which proved to be pathogenic for mice, guinea-pigs, and rabbits. The 

 number of bacteria per cubic metre varied from 1,500 to 3,000,000, the aver- 

 age being about 268,000. The observations were made during the winter 

 months. 



Marpmaiin (1893), in his examination of dust collected in the streets of Leip- 

 zig for tubercle bacilli, obtained positive results from a considerable pro- 

 portion of the specimens examined. Evidently these bacilli in dust from the 

 streets are liable to be blown into the air and deposited upon the mucous 

 membrane of the respiratory passages of those breathing this air. Christian! 

 (1893) has shown that, as a rule, no bacteria are present in the air at an alti- 

 tude of one thousand metres or more above the soil (air collected during 

 balloon ascensions). 



Dyar (1895) has made a careful study of the microorganisms found in. the 

 air in the city of New York. He has described numerous species of micro- 

 cocci and bacilli found chiefly in the air of the hallway of the College of 

 Physicians and Surgeons. Some of these are new and some have been 

 identified as previously described species. 



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