THE BACTERIOPHAGE CORPUSCLE 81 



in the incubator showed only a few traces of bacterial culture, the 

 appearance resembling the agar tube representing the 10~^ dilution of 

 the preceding experiment. As for the agar tubes upon which a drop of 

 the suspension was spread after the bacteriophage had acted for 5 hours 

 or more, none presented any evidence of growth. They were sterile. 

 In appearance these tubes were just the same as were those of the other 

 experiment where the plantings had been derived from the suspensions 

 inoculated with a large amount of bacteriophage liquid. It seems that 

 the bacteriophage was so abundant that the entire surface of the agar 

 forms but a single plaque, or, to express it more correctly, the plaques 

 were so numerous that they touched one another leaving no room for 

 bacterial growth. 



In brief, then, to summarize all of this, bacteriophagy in a liquid 

 medium reveals itself macroscopically by a dissolution of the bacteria 

 contained in the medium, the latter becoming as clear as sterile, unin- 

 oculated bouillon. Upon agar bacteriophagy takes place in the same 

 manner. The agar, at the point where the phenomenon occurs, is bare, 

 without any sign of growth, having the same aspect as a sterile agar 

 slant. In this condition it remains indefinitely (d'HereUe^^"-^^^). 



To mention all the authors who have confirmed these facts would be 

 to enumerate, in fact, almost all who have investigated the phenome- 

 non of bacteriophagy. These facts have not been disputed, although, 

 as we will see, the interpretations of the facts differ very materially. 



These experiments show that the number of "plaques" on agar is 

 related to the quantity of bacteriophage contained in the fluid, but they 

 suggest, in addition, an hypothesis of extreme interest, and one worthy 

 of test for it is burdened with matters of the greatest concern. 



We have seen that when a very great number of bacteria and a very 

 small quantity of the bacteriophage principle are combined and spread 

 upon agar immediately after the inoculation of the bacteriophage, the 

 result, after incubation, is a culture formed by the development of the 

 bacteria distributed upon the agar, and this is spotted with bare areas, 

 or plaques. The small amount of bacteriophage present appears, then, 

 to concentrate its action at particular points (d'Herelle^^°). Can the 

 physical state of the bacteriophage be "discontinuous"? Can this 

 principle exist, in what up to this time we have called a bacteriophage 

 liquid or a bacteriophage filtrate, in particulate form, as corpuscles in 

 suspension? 



