132 PATHOGENIC BACTERIA. 



tubes are connected with a hydrogen generator, and the 

 gas is allowed to pass through until all the oxygen is 

 forced out and replaced by the hydrogen, after which the 

 ends of the tubes are sealed in the flame (Fig. 32). 



lyiborius has designed a special tube for accomplish- 

 ing the same thing. 



Kitasato and Weil found the addition of 0.3-0.5 per 

 cent, of sodium formate to be of use in aiding the rapid- 

 ity of the development of anaerobic cultures. L,iborius 

 found that 2 per cent, of glucose added to the culture- 

 medium also increased the rapidity of the process. 



The methods now generally employed by bacteri- 

 ologists for the anaerobic cultivations embrace all the 

 essentials of the foregoing methods. One of the best 

 arrangements for the purpose is that devised by Dr. 

 Ravenel. His inoculations are deeply made in culture- 

 media as free from air as possible. The tubes are 

 loosely plugged, and are placed in an air-tight cham- 

 ber the bottom of which contains pyrogallic acid py- 

 rogallic acid i, solution of caustic potash i, water 10. 

 The apparatus is connected by two tubes with an ex- 

 haust-pump on one side, and with a hydrogen appara- 

 tus on the other, by which means the atmosphere is ex- 

 hausted, and replaced by hydrogen until only pure hydro- 

 gen remains, after which the chamber is permanently 

 sealed and the germs allowed to grow. Such a chamber 

 can be constructed to hold a number of tubes or Petri 

 dishes, yet not be too large to be stood in an incubator. 

 Whatever oxygen may have escaped the exhaustion or 

 have entered by the process of leakage is at once absorbed 

 by the pyrogallic acid in the lower chamber of the ap- 

 paratus. 



An apparatus for plating out strictly anaerobic bac- 

 teria that has met with great favor is that invented by 

 Botkin (Fig. 34). It combines the replacement of the 

 air by hydrogen and the absorption of the oxygen possi- 

 bly remaining by alkaline pyrogallic acid. In using the 

 apparatus the uncovered Betri dishes are placed one 



