BACTERIA IN 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 pene about 268,000. The observations were made during the winter 
mouths. 
Marpmann (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. Christiani 
(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 microdrganisms 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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