84 



CULTIVATION OF ANAEROBIC BACTERIA. 



stand, and in the lower part of the large tube are placed ten cubic 

 centimetres of a ten-per-cent solution of caustic potash, to which one 

 gramme of pyrogallic acid is added. The absorption of the oxygen 

 takes some time, but, according to Buchner, it is finally so complete 

 that strict anaerobics grow in the small tube. 



In practice, cultivation in an atmosphere of hydrogen will be 

 found the most convenient method, and for this any form of hydro- 

 gen generator may be used. The writer is in the habit of using the 

 form shown in Fig. 56. A perforation a quarter of an inch in 

 diameter is drilled through the bottom of a wide-mouthed bottle. 

 Some fragments of broken glass are then put into the bottle, f orm- 



FIQ. 57. 



ing a layer two or three inches thick. Upon this is placed a quan- 

 tity of granulated zinc. This bottle has a tightly fitting cork, 

 through which passes a metal tube having a stopcock. The bottle 

 is placed in a glass jar containing diluted sulphuric acid (one part 

 by weight of sulphuric acid to eight parts of water). The acid, ris- 

 ing through the perforation in the bottom of the bottle, when it 

 comes in contact with the zinc gives rise to an abundant evolution 

 I hydrogen, which escapes by the tube a when the stopcock is 

 open. When this is closed the gas forces the acid back from con- 

 tact with the zinc. To remove any trace of oxygen present the 

 #as may be passed through a solution of pyrogallic acid in caustic 

 potash. 



Evidently plates prepared by Koch's method, or Esmarch roll 



