EXAMINATION OF AIR AND WATER. 



39 



aeroscope (Fig. 11), which is constructed in the following 

 manner : A bell-shaped vessel, A, is provided with a tube, C, 

 through which air can be aspirated. A hollow cone, shown in 

 the left-hand figure, is screwed into the bottom of A ; the mouth 



FIG. 11. Aeroscope. 



of the cone, B, points downwards ; in the apex, D, of this cone 

 there is a very fine opening through which the air is aspirated, 

 and immediately over this opening is fixed a thin glass-plate 

 covered with a mixture of glycerine and glucose. The parti- 

 cles carried in by the air settle to a great extent on the viscous 

 mixture. The intercepted micro- 

 organisms are distributed as equally 

 as possible on the glass-plate, and 

 counted under the microscope. This 

 method is so far defective in that it 

 gives no information on the most 

 important point, namely, which and 

 how many of the intercepted germs 

 are actually capable of development. 

 In order to determine the number 

 of germs capable of development, and 

 also their nature, MIQUEL employs the 

 following apparatus (Fig. 12). The flask A has fused into 

 it a tube, E, tapering below and nearly reaching to the 

 bottom; the upper end of this is fitted with a ground cap, 

 H, provided with a narrow filter-tube containing sterilised 

 cotton-wool, asbestos, or glass-wool, as. On one side of the 

 flask is a tube, Asp, which is constricted in the middle and is 

 provided with two cotton- wool plugs, w and w. On the other 



FIG. 12. MIQUEL'S Apparatus for 

 air-analysis. 



