100 ATLAS OF BACTERIOLOGY. 



gradually acclimatized the bacilli to a temperature of 

 12 and showed that they could then kill frogs which 

 are kept at 12. 



Temperatures somewhat below the minimum for 

 the variety in question inhibit the development but 

 are not otherwise injurious. Petruschky has recently 

 recommended keeping them in an ice-box (about 

 4-6). He claims that in this way varieties which 

 perish easily can be kept not only alive and capable 

 of proliferation but also virulent, after they have 

 been allowed to grow for two days at a temperature 

 of 20 (streptococci, etc.). 



Temperatures below also act very slowly and 

 injure the different varieties with varying rapidity. 



If temperatures 5 -10 above the best act upon the 

 culture, the latter is injured in various ways. Races 

 of diminished intensity of growth develop, the viru- 

 lence and fermentative power diminish, and the capa- 

 bility of sporulation is gradually lost. The injurious 

 influence sometimes predominates in one direction, 

 sometimes in another. If the maximum temperature 

 is exceeded, the culture dies. For the psychrophilic 

 forms about 37, for the mesophilic forms about 60, 

 for the thermophilic forms 75, are quite rapidly 

 fatal temperatures. No bacterium free from spores 

 can tolerate a temperature of 100 even for a few 

 minutes. 



7. MECHANICAL AND ELECTRICAL EFFECTS. 



:cuttu.ra- are.ma(le, a] most exclusively upon 

 nutri&nffc, tfiedifr .which, a,xe keptrAjuiet; (it is only to 

 secjira abundant sporulation in fluid media, in the 



