66 THE BACTERIOPHAGE AND ITS BEHAVIOR 



Control tubes, lacking the bacteriophage filtrate, show that the staphy- 

 lococcus develops normally in bouillon containing these quantities of 

 collargol. 



Under such conditions bacteriophagy proceeded normally, as rapidly 

 and in as complete a manner, as in plain bouillon, even though the 

 colloidal silver added (2 cc.) was sufficient to give the medium such a 

 deep brown color that it was impossible to see and read print through 

 the layer of fluid. 



As an incidental finding, the following observation is interesting 

 and is in some degree significant. In the control tubes, containing the 

 same quantities of collargol and the same suspension of staphylococci, 

 but without the bacteriophage, after incubation for 24 hours the col- 

 loidal silver was completely fiocculated, forming a black precipitate 

 on the bottom of the tube. In the suspensions inoculated with the 

 bacteriophage no flocculation took 'place, the liquid remained perfectly 

 clear after bacteriophagy, presenting the same aspect as a tube of 

 sterile bouillon to which a comparable amount of collargol was added. 



This experiment has been repeated with B. dysenteriae with the 

 same result. 



In another series of experiments I have used the dry colloidal silver 

 of Heyden, bearing the trade name "Collargolum steril." To 10 cc. 

 of culture medium (the same as that used above) 5 mgm. of the dry 

 collargolum are added, and then enough of a thick suspension, prepared 

 from a young agar growth, of cocci to yield a count of 250 million per 

 cubic centimeter. Finally, 0.05 cc. of a Staphylo-bacteriophage filtrate 

 is added. After 36 hours bacteriophagy is complete; the medium is 

 absolutely clear and of a deep red-brown color. A drop of this spread 

 upon agar yields no growth. 



If performed with B. dysenteriae this experiment gives the same 

 result. 



As a check on these results, it is found that B. dysenteriae, and the 

 staphylococcus as well, grow perfectly well in bouillon containing 

 colloidal silver in the amount employed in the above experiment. 

 The statement is very frequently made that colloidal silver is a power- 

 ful antiseptic. It would seem to be a fair question to ask how experi- 

 ments should be conducted to demonstrate this fact. Unquestionably, 

 several authors have published experiments tending to show that the 

 bacteriophage is destroyed by the presence of negative colloids, of 

 colloidal silver in particular, but, as a matter of fact, far from being 

 destroyed, the bacteriophage develops normally in the presence of 

 this substance. 



