AIR ANALYSIS. 



439 



The apparatus employed by him consists essentially 

 of three parts : 



(1) A glass tube of a special form to which the name 

 aerobioscope has been given. 



(2) A stout copper cylinder of about sixteen litres 

 capacity, provided with a vacuum-gauge. 



(3) An air-pump. 



Fig. 92. 



Sedgwick's aerobioscope. 



The aerobioscope (Fig. 92) is about .Jo cm. in its 

 entire length ; it is 15 cm. long and 4.5 cm. in diameter 

 at its expanded part ; one end of the expanded part is 

 narrowed down to a neck 2.5 cm. in diameter and 2.5 

 cm. long. To the other end is fused a glass tube 15 

 cm. long and 0.5 cm. inside diameter, in which is to be 

 placed the filtering material. 



Upon this narrow tube, 5 cm. from the lower end, a 

 mark is made with a file, and up to this mark a small 

 roll of brass-wire gauze (a) is inserted ; this serves as a 

 stop for the filtering material which is to be placed over 

 it. Beneath the gauze (at 6), and also at the large end 

 (e), the apparatus is plugged with cotton. When thor- 

 oughly cleaned, dried, and plugged, the apparatus is to 

 be sterilized in the hot-air sterilizer. When cool, the 

 cotton plug is removed from the large end (c), and 

 sterilized No. 50 granulated sugar is poured in until 

 it jusj fills the 10 cm. (d) of the narrow tube above 

 the wire gauze. This column of sugar is the filtering 

 material employed to engage and retain tlie bacteria. 



