EXERCISE XX. 



MAKING CULTURES OF ANAEROBIC BACTERIA. 



77. Explanatory note. Anaerobic bacteria will not 

 grow in the presence of oxygen (atmosphere) and conse- 

 quently they must be cultivated in a medium from which 

 the air has been expelled, or in the presence of some neutral 

 gas such as hydrogen. The known important pathogenic 

 anaerobic bacteria are those of symptomatic anthrax, 

 tetanus and malignant oedema. These are known as obli- 

 gatory anaerobes because they require the absence of oxygen. 

 Others such as Bacillus typhosus are known as facultative 

 anaerobes as they will multiply in media with or without 

 atmospheric oxygen. 



There are several methods of cultivating anaerobic bac- 

 teria but as a rule they are difficult and can not be easily 

 handled in a general course. Two of the simpler processes, 

 however, will be tried. 



78. General Directions. Inoculate a tube of agar 

 after L,iborius' method for anaerobic bacteria from the 

 culture furnished. 



Inoculate 2 fermentation tubes from the same culture. 

 One of the fermentation tubes should contain sugar free 

 bouillon (furnished) the other bouillon containing i% glu- 

 cose. 



Inoculate for study at the next Exercise 2 tubes of liquid 

 agar, (one plain and one containing glucose), a fermentation 

 tube of sugar free bouillon and one containing i % glucose 

 bouillon with B. coli communis from a culture furnished. 



79. Liborius' method. liquefy two tubes of agar and 

 carefully pour them together. After this boil the medium 

 for at least five minutes to expel the air, cool it down to a 

 temperature of 45 C. and then inoculate it from the cul- 



