BACTERIOLOGICAL APPARATUS 



57 



is used almost entirely for sterilizing media etc., while 

 in others it is employed very little and in its place stream- 

 ing steam sterilizers or large water baths are substituted. 

 Temperatures slightly above that of boiling water (100 C.) 

 may be obtained by using instead of an expensive autoclave 

 a water-bath containing a solution of calcium chloride or 

 some other salt. 



Most bacteria that are pathogenic for animals are.culti- 



o 



Fig. 20. Fig. 21. 



Fig. 20. Platinum wires and loops of different forms and sizes 

 used for making cultures. 



Fig. 21. Novy's apparatus for plate cultures in a vacuum or in 

 the presence of hydrogen. In this case hydrogen is introduced 

 through the glass tube and after the atmosphere has been replaced by 

 hydrogen the entrance and exit are closed by turning the stopper. 

 Novy has designed a somewhat similar apparatus for culture tubes. 



vated at a temperature of about 37 C. For this purpose an 

 incubator is necessary. Incubators are constructed on dif- 

 ferent plans, the chamber of some being surrounded by 

 water jackets and others being kept at a constant temperature 

 by means of a circulation of heated air through metal pipes. 

 In some laboratories a small room is kept at the body tem- 

 perature and used in place of an incubator. An apartment 

 incubator for use when a number of individuals are at work 



