AIR ANALYSIS. 441 



When all the sugar is thus shaken down into this part 

 of the apparatus, about 20 c.c. of liquefied, sterilized 

 gelatin is poured in through the opening at the end c, 

 the sugar dissolves, and the whole is then rolled on ice, 

 just as is done in the preparation of an ordinary 

 Esmarch tube. 



Fig. 93. 



Bent funnel for use with aerobioacope. 



The gelatin is most easily poured into the aerobio- 

 seope by the use of a small, sterilized, cylindrical funnel 

 (Fig. 93), 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 

 contamination, carry the tubes to the laboratory, where 

 the cultivation part of the work may be done. 



Aside from this advantage, the filter being soluble, only 

 the insoluble bacteria are left imbedded in the gelatin. 



