190 BACTERIOLOGY. 



32), the stem of which is bent to an angle of about 110 

 with the long axis of the body. 



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 make these 

 analyses at any place, and can, without fear of con- 

 tamination, carry the tubes to the laboratory, where the 

 cultivation part of the work may be done. 



FIG. 32. 



Aside from this advantage, the use of a vacuum- 

 cylinder permits a known volume of air to be aspirated 

 with great ease, and its rate of flow through the filter 

 regulated to a nicety. 



The filter being soluble, only the insoluble bacteria 

 are left imbedded in the gelatin. 



For general use this method is to be preferred to the 

 others that have been mentioned. 



