62 THE BACTERIOPHAGE AND ITS BEHAVIOR 



phage. The results thus obtained will show the extreme limits within 

 which the phenomenon can occur, and it will show at the same time 

 how vain it is to attempt, from a single experiment, to fix the hmiting 

 conditions or the optimal conditions for the reaction, since these vary 

 for each race of the bacteriophage which acts, and for each bacterial 

 strain subjected to its action. 



As far as temperature relationships are concerned, experiment demon- 

 strates that the minimal temperature permitting a typical bacteri- 

 ophagy, that is to say, the lowest temperature at which the final result 

 is a complete dissolution of all of the bacterial cells contained in a 

 suspension subjected to test, is found at about 8°C. (with B. dysen- 

 teriae, d'Herelle'^^). The maximum temperature observed up to the 

 present time is 46°C. (with B. coli, d'Herelle). This by no means 

 implies that subsequent experiments will not extend these limits. 



I have specifically stated that these limits are those which are com- 

 patible with a total dissolution of the bacterial cells. Above and below 

 these Hmits bacteriophagy may still be effected, but the dissolution is 

 only partial. Having available a race of bacteriophage, active against 

 B. dysenteriae, whose upper limit for total dissolution was 41°C., it 

 has been possible to effect several serial passages at 44°, in spite of the 

 fact that at this temperature a dissolution of the bacteria could not 

 be detected macroscopically. But despite this apparent lack of activity 

 bacteriophagy took place, since the active principle, the bacteriophage, 

 regenerated itself, and this in itseK affords proof that destruction had 

 not taken place. 



As regards the optimal temperature, that is to say, that at which 

 the phenomenon manifests itself most quickly and most completely, 

 basing my statements upon the results of my experiments with B. 

 dysenteriae and B. typhosus, I had concluded that the temperature most 

 favorable for bacteriophagy was that which was likewise most favorable 

 for the development of the bacteria. The results of many subsequent 

 experiments, performed with a variety of bacterial species, indicate 

 that this conclusion may have been too restricted. As a general rule, 

 the statement is certainly true for the bacteriophagy of B. dysenteriae 

 and B. typhosus, but it is not equally true for all other species of bacteria. 



The optimum growth temperature for several different strains of the 

 staphylococcus with which I have worked has been found to be at 

 about 37 to 38°C. With three different races of the bacteriophage 

 the reaction was effected with these strains in a perfect manner at 

 between 32 and 34°C., with another race of bacteriophage complete 

 dissolution occurred only at 37°C. 



