PROPERTIES OF THE BACTERIOPHAGE 295 



of the bacteriophage the temperature of inactivation differs for each 

 of the bacteria attacked, and may even be different for a single bacterium 

 and a single bacteriophage from one experiment to another. Other 

 investigators have obtained comparable results. 



The following experiment shows that these variations are related 

 to the actual intensity of the virulence for each bacterium attacked. 



A race of the bacteriophage was isolated from the feces of a patient 

 convalescent from benign infectious jaundice. During the febrile period 

 in this case the intestinal B. coli had been almost completely replaced by 

 B. enteritidis. This bacteriophage was first subjected to 12 passages 

 at the expense of B. enteritidis (isolated from the stools of the patient 

 at the onset of the disease). Following these 12 passages (each one 

 being effected by inoculating 0.001 cc. of the suspension previously 

 bacteriophaged into 10 cc. of fresh suspension) a selective isolation was 

 made, in order to eliminate any other races of the bacteriophage which 

 might possibly have been carried along from the fecal filtrate. 



This pure bacteriophage showed virulences as follows: 



B. enteritidis (strain from the patient) + + + + 



B. coli (strain from the patient) + + + 



B. dysenteriae Shiga + + + + 



B. paratyphosus A + 



B. paratyphosus B + + 



Sealed ampoules containing this bacteriophage were immersed for 30 

 minutes* in a water-bath regulated at the following temperatures: 

 60, 63, 65, 68, 70, 73, 75, and 78°C. A drop from each of these heated 

 suspensions was added to a tube containing a suspension of susceptible 

 bacteria, and the virulence was determined by the simphfied procedure 

 discussed in the section on "Evaluation of Virulence." (See table 27.) 



It is not surprising then that those who have studied the resistance 

 of different races of the bacteriophage to heat have obtained different 

 figures for each race of bacteriophage, since everything depends upon 

 the virulence. 



Some authors (Weinberg and Aznar,''^^ Tchang Kouo Ngen and 

 Wagemans^^^) have stated that the bacteriophage is destroyed only 

 at a temperature of 80°C. I am inchned to believe that their technic 

 must have been defective for in accord with the majority of those who 

 have pubhshed on the subject I have never yet found a bacteriophage, 



* The ampoules were made of drawn out Pasteur pipettes, with thin walls, 

 thus permitting the contents to quickly reach the temperature of the water-bath. 

 This method is the only one which is free of criticism. 



