134 BACTERIOLOGY 



Further Anaerobic Methods. — Numerous other expedients 

 Tiave been employed for the cultivation of anaerobes. Koch 

 covered part of the surface of a gelatin plate with a bit of steril- 

 ized mica or a cover-glass. Such a method suffices to prevent the 

 growth of strictly aerobic forms but rarely suffices for the success- 

 ful culture of strict anaerobes. Covering the surface of the 

 medium with sterile liquid paraffin is a more perfect means of 

 excluding air. 



In all anaerobic culture methods, the presence of one or more 

 reducing substances in the culture medium is of great importance. 

 Those commonly employed are glucose, litmus and native protein. 



