630 APPLICATION OF METHODS OF BACTERIOLOGY 



with a stopcock on the cylinder, or to a glass tube tightly 

 fixed in the neck of an aspirating-bottle by means of a 

 perforated rubber stopper. The cotton plug is then moved 

 from the upper end of the aerobioscope, and the desired 

 amount of air is aspirated through the sugar. Dust-par- 

 ticles and bacteria will be held back by the sugar. During 

 manipulation the cotton plug is to be protected from con- 

 tamination. 



FIG. 113 



Bent funnel for use with aerobioscope. 



When the required^ amount of air has been aspirated 

 through the sugar the cotton plug is replaced, and by gently 

 tapping the aerobioscope while held in an almost horizontal 

 position the sugar, and with it, the bacteria, are brought 

 into the large part (e) of the apparatus. 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 



