86 



^^PIRAL 7'TT7>ST AND OPT. ACT I \ IT Y 



ciation" botli dextral, DR, and sinistral, LR, strains of 

 Bacillus mycoides develop into smooth ones, which form, 

 on growing on solid medium, flat spherical colonies, LS 

 and DS (for literature see Arkwright, 1930). The study of 

 the action of temperature was made according to the pre- 

 vious plan. It was found that the phenomenon of heat 

 injury characteristic of the dextral strains was about as 

 marked in the S-f orms as in the R-f orms. 



It was decided then to try the experiment with the 

 DS and LS strains in liquid medium. The rate of growth 

 was now determined by a bacterial count in a Thoma 

 chamber, under the microscope, forty hours after the 

 inoculation. The relation of growth to temperature is 

 represented in Figure 7. One sees that in the dextral 

 strain the characteristic heat injury appears in the range 

 of temperatures extending' from 24° to 28° C. 



Similar results were thus obtained with the R-forms, 

 with the S-forms and on liquid as well as on solid culture 



200 



I 50 



100 - 



Fig. 7. Growth-temperature relation in dextral (DS) and sinistral 

 (LS) strains of Bacillus ^nycoides, grown on liquid medium. Abscissae: 

 Temperature in degrees C; Ordinates: Number of cells per 1/160 cc. 

 (From Gause, 1939.) 



