DIFFERENTIAL ATMOSPHERE CULTIVATION 



2 57 



the centre will be equally efficient). The interior 

 of the vessel is partly filled with water and covered with 

 a lid which is perforated for a thermometer. This 

 latter .dips into the water and records its temperature. 

 A very small Bunsen flame under the apparatus suffices 

 to keep the benzole boiling and the water within at a 

 constant temperature of 80 C. The bath is thus always 

 ready for use. 



METHOD. To use the apparatus. 



1 . Place some of the mixture itself, 

 if fluid, containing the spores, or an 

 emulsion of the same if derived 

 from solid material, in a test-tube. 



2. Immerse the test-tube in the 

 water contained in the benzole bath, 

 taking care that the upper level of 

 the liquid in the tube is at least 2 

 cm. beneath the surface of the water 

 in the copper vessel. 



3. The temperature of the water, 

 of course, falls a few degrees after 

 opening the bath and introducing a 

 tube of colder liquid, but after a few 

 minutes the temperature will have 

 again reached 80 C. 



4. When the thermometer again 

 records 80 C., note the time, and 

 fifteen minutes later remove the tube 

 containing the mixture from the bath. 



5. Make cultures upon suitable media; incubate. 



7. Differential Atmosphere Cultivation. 



(a) By adapting the atmospheric conditions to the 

 particular organism it is desired to isolate, it is com- 

 paratively easy to separate a strict aerobe from a 

 strict anaerobe, and vice versa. In the first case, 

 however, it is important that the cultivations should 

 17 



FIG. 140. Benzole 

 bath. 



