EXAMINATION OF AIR AND WATER. 39 



end. The flask is charged with distilled water, and the whole 

 apparatus sterilised. When the apparatus is to be employed, 

 the tube Asp is connected with an aspirator ; for instance, a 

 bottle filled with water and provided with a cock below ; the 

 cap H is taken off, and the air then passes, bubble by bubble, 

 through the opening o, through the water g, and out through 

 the cotton-wool plugs of the tube Asp. Since all the germs 

 of the air are not retained by the water when the air-bubbles 

 ascend through the latter, the cotton-wool plug w is intended 

 to catch those which get past the water. When the experiment 

 is finished, the cap H is replaced over the tube K. By blowing 

 through Asp, the liquid is made to ascend in R in order that 



FIG. 9. 

 Miquel's Apparatus for Air-Analyses. 



any germs which may have settled on the walls of the tube 

 may be washed down into the liquid. Then, by blowing with 

 greater force, the inner cotton-wool plug w is driven down 

 into the liquid, and its germs shaken off into the latter. After 

 sterilising the thin tube B in a flame, the point is nipped off, 

 and the liquid is now by blowing through Asp transferred, 

 drop by drop, into a large number of flasks containing 

 sterilised broth. 



The main point here is, by means of preparatory experi- 

 ments, to obtain such a dilution of the air-infected water 

 that a considerable proportion of the small flasks (one-half 

 for example) remain sterile after inoculation; or several 

 samples of the water may be diluted to different degrees, 



