150 THE BACTERIOPHAGE 



I ought in this connection to dwell upon the action of tempera- 

 ture, since some authors have suggested that the temperature 

 of destruction of the bacteriophage was too high to allow a con- 

 sideration of them as living beings. It is thus necessary to re- 

 call some of the elementary facts which readers of this work cer- 

 tainly ought not to ignore. The lethal temperature, as we have 

 seen, is about 75°C. Without mentioning the living organisms 

 from thermic sources, of which the temperature reaches up to 

 93°C, it is known that one may readily isolate from sewage bac- 

 teria which develop normally at a temperature of 75°C. More- 

 over, Duclaux has shown that the young cells of Tyroihrix tenuis 

 do not die until a temperature of about 100°C. has been reached. 

 A lethal temperature of 75°C, far from being exceptional, must 

 be recognized as well below that resisted by a large number of 

 unicellular organisms. 



In so far as the action of antiseptics is concerned, the bacterio- 

 phage takes a position intermediate between the bacteria in their 

 vegetative form and the spores derived from these bacteria. 

 More resistant than the first, they are more sensitive than the sec- 

 ond. Compared from this point of view with other known ultra- 

 microbes, they are definitely more susceptible than some. The 

 virus of the tobacco mosaic, for example, will resist for several 

 months a concentration of alcohol which will kill the bacteriophage 

 in a short time. The virus of rabies, and that of vaccinia, 

 remain alive in concentrations of glycerine that destroy the 

 bacteriophage. 



It is to be noted that the bacteriophage presents the character- 

 istic of being particularly sensitive to certain reagents which 

 have absolutely no effect upon the diastases; quinine for example. 

 As for glycerine, which destroys the bacteriophage, it constitutes 

 the medium of choice for the indefinite preservation of bacterial 

 toxins and the most sensitive diastases. 



3. With sufficiently active strains of the bacteriophage a com- 

 plete and permanent lysis is secured; all of the bacteria contained 

 in a suspension are definitely destroyed. Moreover, serial 

 passages of the bacteriophage are possible in bacterial suspensions 

 made in fluids which do not permit the development of these 

 bacteria; — physiological salt solution, or bouillon with forty per 



