PROPERTIES OF THE BACTERIOPHAGE 305 



tions were all of a diameter, about 2 mm. The spreading corresponding 

 to the 0.75 cc. dilution of the quinine salt gave, as indicated above, from 

 10 to 15 plaques, but here the plaques varied greatly in size, some having 

 a diameter of about 2 mm., others being far smaller. 



But whatever may be the significance of this variability in plaque 

 formation, it clearly appears that the bacteriophage is either destroyed 

 or rendered avirulent after 24 hours in a 1 per cent solution of quinine 

 hydrochloride.* 



Just as for all antiseptic agents which have been tested, Watanabe'^^ 

 found that different races of the bacteriophage show a variable degree 

 of resistance for the salts of quinine. Destruction, or rather, as we have 

 seen, avirulence is accomplished within 24 hours by the addition of 

 from 5 to 50 per cent of a 10 per cent solution of quinine hydrochloride. 



Wolff and Janzen''^^ have worked with a number of the quinine 

 derivatives,^ — optochin, eucupine, vucine, and chinosol. To bacterio- 

 phage filtrates mixed with a suspension of a susceptible bacterium 

 they added variable amounts of these antiseptics and found that at a 

 certain concentration (with chinosol, 1:600) the mixture when spread 

 on agar no longer gave plaques. At first sight it would seem that the 

 corpuscles are here destroyed, but this is not the case. The corpuscles 

 have simply become "latent." They have lost all activity for the 

 bacterium, but they are not destroyed, for it is only necessary to add a 

 drop of this mixture to a fresh suspension of the susceptible bacterium 

 and to spread this over agar to obtain characteristic plaques. They 

 performed this experiment with B. coli, B. typhosus, B. dysenteriae, 

 and with the staphylococcus, using four races of the bacteriophage. 



The result here is comparable to that which I observed with sodium 

 fluoride, where also a quantity of antiseptic insufficient to kill the 

 bacteria, even allowing their development, completely inhibited the 

 bacteriophage corpuscles. 



Malachite green, yatren, rivanol, and trypaflavine gave Wolff and 

 Janzen similar results. And they further noted that in the presence of 

 very minute quantities of the antiseptics (chinosol, 1 : 4000) the develop- 



* Stimulated by these results reported by Eliava and Pozerski, Brocq- 

 Rousseu, Urbain, and Forgeot have tested the activity of quinine salts for the 

 streptococcus of equine strangles. They have seen that, just as with the bac- 

 teriophage, the streptococcus underwent an attenuation of virulence, passing to 

 a complete lack of virulence, in the presence of quinine salts. The death of the 

 streptococcus ultimately occurs, but only if the time of contact is prolonged 

 beyond that necessary to cause a complete loss of virulence (Ann. Inst. Pasteur, 

 1923,37,322). 



