BACTERIA OF THE AIR 625 



Several methods have been proposed for the estimation of the num- 

 ber of bacteria in the air; that of Winslow, 1 which consists essentially 

 in aspirating a definite volume of air through two flasks, each of which 

 contains melted nutrient gelatin, is the simplest and most direct. 

 Comparatively little has been accomplished thus far from a quantita- 

 tive study of the bacterial population of the air; it is possible that 

 an attempt to isolate specific types of pathogenic bacteria from 

 theatres and other places where large numbers of people meet might 

 throw some light upon certain features of the air transmission of 

 bacterial infections which are not well understood at the present time. 



1 Science, 1908, xxviii. 28. 



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