108 THE BACTERIOPHAGE AND ITS BEHAVIOR 



see that a Typho-bacteriophage, and this is also true for a CoH-bacterio- 

 phage or a Staphylo-bacteriophage, is as a rule not active upon all 

 strains of B. typhosus; certain strains being susceptible while others 

 are naturally resistant. This is what I have meant when a bacterial 

 species has been termed heterogeneous toward a bacteriophage. To 

 return to the exception mentioned above, Janzen and Wolff""* have 

 reported that a Typho-bacteriophage may be fixed to typhoid bacilli 

 of strains against which this Typho-bacteriophage is inert. This must 

 be regarded as an exceptional case, for Jaumain and Meulemans"^ 

 have shown with different races of Coli-bacteriophage and Staphylo- 

 bacteriophage that fixation does not occur with bacteria belonging to 

 insusceptible strains. My own observations agree with those of 

 Janzen and Wolff, for I have observed a fixation, although but partial 

 (it is, however, the same when these races act upon susceptible bac- 

 teria, it being simply a question of degree), with insusceptible staphy- 

 lococci. We will see shortly that this is also what happened in some 

 experiments reported by Flu. 



As a modification of the above experiments da Costa Cruz^'^^ has 

 shown that fixation takes place upon heat-killed bacteria, provided 

 they were of a susceptible strain. Working with a Flexner-bacteriophage 

 he has seen that the corpuscles are fixed to dysentery bacilli which 

 have been killed by heating at 60°C., but that they are not fixed to 

 staphylococci, also killed at the same temperature. This has been 

 confirmed by several authors. 



Prausnitz and Firle^^^ have seen that fixation took place with sus- 

 ceptible bacteria after they had been heated at 60, 70, 80, 90 and 100°, 

 but that it did not take place when the bacteria had been exposed to 

 a temperature of 120°C. 



These observations warrant the conclusion that fixation proceeds in 

 the same manner whether the susceptible bacteria are Uving or dead, 

 although the bacteriophage corpuscles can develop only at the expense 

 of the former. 



These facts make clear the reason for the delay in bacteriophagy 

 caused by the viscosity of the medium, whether this viscosity is due to 

 gelatin, to a gum, or to any other substance which is, of itself, without 

 action upon the phenomenon. When we place bacteria and bacterio- 

 phage corpuscles within a liquid it is evident that inasmuch as the first 

 act of bacteriophagy consists in a fixation of the corpuscles to the 

 bacterial cells, these corpuscles must first of all traverse the distance 

 which separates them from the nearest bacteria. This necessitates 



