THE MECHANISM OF BACTERIOPHAGY 135 



tion of the bacteriophage corpuscle must be different from that of the 

 substance of the bacterium within which it multiples. And it violates 

 no fundamental principle to assume that the corpuscle can be visible 

 when found enclosed within the substance of the bacterium or even in 

 the floccules before they dissolve, and that it may cease to be visible 

 just as soon as these floccules are dissolved. However this may be, 

 the visibility of the bacteriophage corpuscle within the bacterium is 

 only an hypothesis, but it is a plausible and possibly a probable hy- 

 pothesis. 



In concluding this section we may call attention to two facts which 

 tend to show that, under the action of the bacteriophage, the electrical 

 potential of the bacteria (which are, as we know, negatively charged) 

 is diminished. In the first place it can readily be shown that their 

 affinity for basic dyes is reduced, and in the second place, very frequently 

 an agglutination takes place; the bacteria flocculate under the action 

 of the bacteriophage. Flocculation results from an increase in the 

 surface tension, associated with a reduction in charge. 



RESUME 



The bacteriophage corpuscle is unable to multiply in any medium in 

 the absence of living and normal bacteria. The bacterial cell con- 

 stitutes the sole culture medium for the bacteriophage (d'Herelle^^"). 

 An experiment of WoUmann^^^ suggests that development, to some de- 

 gree, may occur in the presence of diffusible bacterial products. 



The first act of bacteriophagy consists in the approach of the bac- 

 teriophage corpuscle toward the bacteria, then in the fixation of the 

 corpuscle to the latter (d'Herelle^^^). The rapidity with which fixation 

 takes place depends upon various factors; principally upon the degree 

 of activity of the bacteriophage. Fixation is the more rapid the higher 

 the virulence of the bacteriophage corpuscle. 



The fixation is specific, that is to say, that it takes place only with 

 susceptible bacteria (d'Herelle^-0> and it may occur even if the bacteria 

 are dead (da Costa Cruz^^^). There is, however, an exception to this; 

 the bacteriophage corpuscle fixes itself upon a bacterium naturally 

 refractory to the action of this bacteriophage provided the latter at- 

 tacks other strains of bacteria belonging to the same species (Janzen 

 and Wolff^^^). This is not true for bacteria with an acquired resistance. 



The bacteriophage corpuscle penetrates into the interior of the 

 bacterial cell. When, as a result of its faculty of multiplication, the 

 bacteriophage corpuscle which has penetrated into the bacterium forms 



