298 METHODS OF IDENTIFICATION AND STUDY 



II. Temperature. 



(A) Range. 



1. Prepare a series of ten tube cultivations, in fluid 

 media, of optimum reaction. 



2. Arrange a series of incubators at fixed tempera- 

 tures, varying 5C. and including temperatures between 

 5 C. and 50 C. 



(In the absence of a sufficient number of incubators 

 utilise the water-bath employed in testing the thermal 

 death-point of vegetative forms.) 



3. Incubate one tube cultivation of the organism 

 aerobically or anaerobically, as may be necessary, in 

 each incubator, and examine at half -hour intervals for 

 from five to eighteen hours. 



4. Note that temperature at which growth is first 

 observed macroscopically (Optimum temperature). 



5. Continue the incubation until the completion of 

 seven days. Note the extremes of temperature at 

 which growth takes place (Range of temperature). 



6. Control these results if considered necessary 

 arranging the series of incubators to include each degree 

 centigrade for five degrees beyond each of the extremes 

 previously noted. 



(B) Optimum. 



1. Prepare a second series of ten tube cultivations 

 under similar conditions as to reaction of medium. 



2. Incubate in a series of incubators in which the 

 temperature is regulated at intervals of i C. for five 

 degrees on either side of optimum temperature observed 

 in the previous experiment (A, step 4). 



3. Observe again at half -hour intervals and note that 

 temperature at which growth is first visible to the 

 naked eye= Optimum temperature. 



(C) Thermal Death-point (t. d. p.) 

 Moist Vegetative Forms : 



The /. d. p. here is that temperature which with 



