PROPERTIES OF THE BACTERIOPHAGE 291 



dium). From my own work I feel warranted in definitely contradicting 

 this. It is probable, as I have stated above, that de Necker carried 

 out his experiments with the materials in an acid medium. 



Contributory evidence on this point is afforded by some experiments 

 with colloidal silver. For example, I have added 10 mgm, of "CoUar- 

 golum siccum" of Heyden to 10 cc. of a suspension of Staphylo-bac- 

 teriophage. Titrations of these corpuscles made 13 months later showed 

 that the bacteriophage had not lost its virulence. Determinations 

 of the same kind made with a Shiga-bacteriophage, yielded the same 

 result. 



Moreover, some of the experiments reported in Chapter I may be 

 recalled, showing that bacteriophagy takes place normally in bouillon, 

 at a pH of 7.8, containing 5 mgm. of dry collargol to each 10 cc* 



As for the so-called inhibitory action of the colloid gelatin, I think 

 that I have shown by the experiments detailed in Part I, that the 

 inhibitory effect manifested is of a wholly different nature. In a liquid 

 medium gelatin is inhibitory because of its viscosity (Hauduroy), on a 

 solid medium because the gel does not permit the diffusion of the 

 products resulting from bacteriophagy, products which impede the 

 activity of the bacteriophage itself. 



For purposes of comparison it is interesting to note that Valee and 

 Carre have observed that different ultraviruses, that of aphthous fever 

 in particular, are strongly adsorbed by red blood cells, and that Levaditi 

 and Nicolau*^^ have reported that the ultravirus of vaccinia is adsorbed 

 by animal charcoal and by the serum globuhns. 



5. EFFECTS OF IRRADIATION 



Appehnans'^'* states that a suspension of the bacteriophage subjected 

 to ultraviolet rays is inactivated by an exposure of ten minutes. 



According to Gildemeister,^^^ the sensitivity of the bacteriophage 

 toward ultraviolet rays is the same as that of the bacteria. 



Zoeller^*'' observed a complete inactivation after 15 minutes of 

 exposure. 



Gerretsen, Gryns, Sack, and Sohngen,^^^ working with a bacteriophage 

 virulent for B. radicicola, have exposed at a distance of 30 cm., either 



* De Necker also states that aluminium hydroxide causes a flocculation of the 

 bacteriophage. When the precipitate is dissolved by the careful addition of 

 acetic acid the bacteriophage reappears in the liquid. Flocculation was never 

 complete. A possible error in this experiment is the occlusion of the pores 

 of the candle used to filter the precipitated hydroxyl-bacteriophage. 



