BACTERIA IN THE AIR. 551 



air of the country ; the lower strata of the atmosphere contained 

 more than the air of elevated localities. 



Von Freudenreich also found that the air of the country contained 

 fewer germs than that of the city. Thus in the city of Berne a cubic 

 metre of air often contained as many as two thousand four hundred 

 germs, while the maximum in country air was three hundred. His re- 

 sults corresponded with those of Miquel in showing that the number 

 of atmospheric organisms is greater in the morning and the evening, 

 between the hours of 6 and 8, than during the rest of the day. Neu- 

 mann, whose researches were made in the Moabite Hospital, found 

 the greatest number of bacteria in the air in the morning after the 

 patients able to sit up had left their beds and the wards had been 

 swept. The number of germs was then from eighty to one hundred 

 and forty in ten litres of air, while in the evening the number fell to 

 four to ten germs in ten litres. 



Miquel has given the following summary of results obtained in 

 his extended experiments, made in Paris during the years 1881, 1882, 

 and 1883 : 



Rue de Rivoli, average for one year, 750 ; summit of Pantheon, 28 ; 

 Hotel-Dieu, 1880, average for four months, male ward 6,300, female 

 ward 5,120 ; La Piete Hospital, average of fifteen months, 11,100. 



It must be remembered that the figures given relate both to bac- 

 teria and to the spores of mould fungi, and that the latter are com- 

 monly the most numerous when the experiment is made in the open 

 air. Petri has shown that when gelatin plates are exposed in the air 

 the relative number of spores of mould fungi deposited upon them is 

 less than is obtained in aspiration experiments. 



The number of colonies which develop on exposed plates does not 

 represent the full number of bacteria deposited, for these colonies 

 very frequently have their origin in a dust particle to which several 

 bacteria are attached, or in a little mass of organic material contain- 

 ing a considerable number. 



It is generally conceded that sea air and country air are more 

 wholesome than the air of cities, and especially of crowded apart- 

 ments, in which the number of bacteria has been shown to be very 

 much greater. But it would be a mistake to ascribe the sanitary 

 value of sea, country, and mountain air to the relatively small num- 



