BACTERIOLOGICAL ANALYSTS OF AIR. G09 



The larger part of the aerobioscope is divided into 

 squares to facilitate the counting of the colonies. 



By the employment of this apparatus one can iSlter 

 the air at any place, and can then, without fear of con- 

 tamination, carry the tubes to the laboratory and com- 

 plete the analysis. Aside from this advantage, the filter 



Fig. 110. 



Bent funnel for use with aerobioscope. 



being soluble only the insoluble bacteria are left im- 

 bedded in the gelatin. 



For general use this method is to be preferred to the 

 others that have been mentioned. 



BACTERIOLOGICAL STUDY OF THE SOIL. 



Bacteriological study of the soil may be made by 

 either breaking up small particles of earth in liquefied 

 media and making plates directly from this ; or by wliat 

 is perhaps a better method, as it gets rid of insoluble 

 particles which may give rise to errors : breaking up 



39 



