CLINICAL BACTERIOLOGY. 



CULTIVATION OF ANAEROBIC BACTERIA. 



Anaerobic bacteria may be facultative or obligate. The 

 former may develop also in the presence of oxygen, 

 although but sparingly. The latter require special cultural 

 methods. The cultivation of strictly anaerobic bacteria is 

 undertaken either in a room free from air, or in an atmos- 

 phere of indifferent gas as, for instance, hydrogen or 

 with the employment of substances that absorb oxygen, or, 

 finally, by means of stab-culture in a high layer. The 

 usual culture-media are employed, but with the addition of 



Fig. 28. Frankel's method of making 

 anaerobic cultures. 



Fig. 29. Hesse's method of making 

 anaerobic cultures. 



two per cent, of grape-sugar, as all of the anaerobic bacteria 

 thus far known form from this substance gas in abundance 

 (carbon dioxid, hydrogen sulphid, methane, mercaptan, 

 etc.), in this way displacing the oxygen of the air. 



Plate-cultures. According to a method devised by R. 

 Koch, a sheet of mica, sterilized by heat, is placed upon the 

 liquid gelatin spread upon the plate. After solidification has 

 taken place the gelatin is thus rendered air-tight, and be- 

 neath the mica the anaerobic colonies undergo development. 

 It is more serviceable in the preparation of anaerobic plates to 



