THE MICROSCOPE. 



"5 



for Mr. Miquel has characterized a bacterium which resisted a tem- 

 perature of 1 45 for two hours. 



Yet heat offers one drawback, and that is that itweakens the nu- 

 tritive properties of the organic liquids. An effort has therefore been 

 made to dispense with it and to substitute for it a filtration through 

 porous substances. For this purpose Mr. Miquel has used at Mont- 

 souris the apparatus shown in Fig. 5. This consists of a glass bulb, 

 d, with a long neck, /, having a lateral tubulure, /, and being sur- 

 mounted with a funnel, e. 



Plaster and asbestos having been placed in the funnel, the bulb 

 is raised to a high temperature in a stove, and sterilized water is then 

 introduced through the tubulure, /, and raised to the boiling point. 



I , '■' . T/A 



Fig. 5. 



Before the water has entirely disappeared the tubulure is closed by 

 means of a blowpipe, and, when a cooling occurs, a vacuum is pro- 

 duced in the bulb. The broth, being poured in a cold state over 

 the mixture of plaster and asbestos, filters slowly through it, depos- 

 its its germs therein, and enters the bulb absolutely devoid of 

 organisms. 



During summer, in order to prevent putrefaction, the funnel and 

 vessel, V (Fig. 6), are surrounded with ice. This cold process suc- 

 ceeds better than any other tending to the same end. 



The sowing of atmospheric germs in nutritive liquids is done 

 by means of special matrasses resembling in form those used by Mr. 



