BACTERIOPHAGY IN A FLUID MEDIUM 67 



May not the erroneous conclusions reached by these authors be due 

 to the fact that they have used commercial solutions of colloidal silver 

 to which some antiseptic agent had been added, and have they not 

 attributed to colloidal silver an effect which was due to some agent of 

 whose presence they were unaware? Obviously, we can not tell. 

 But in any case, a considerable number of experiments warrant the 

 statement that pure colloidal silver (Collargolum siccum, Heyden,* 

 for example) exercises no antiseptic action upon the colon-typhoid- 

 dysentery group of bacilli or upon the staphylococci, and that in its 

 presence bacteriophagy occurs normally.f 



Colloidal suKur, another electro-negative colloid, has also been 

 tested. In its presence bacteriophagy takes place in an absolutely 

 normal fashion. Indeed, with this colloid it would seem that bacteri- 

 ophagy is, if anything, stimulated, as has been observed by Otto and 

 Munter.494J 



In brief, then, negative colloids, and these are the only ones which 

 can be tested, since bacteriophagy will not take place in an acid medium, 

 cause, of themselves, no effect upon the phenomenon of bacteriophagy. 



Dyestuffs 



Five-hundredths of a cubic centimeter of a Staphylo-bacteriophage 

 is added to 10 cc. of a suspension (100 million cocci per cubic centi- 

 meter) of Staphylococcus aureus. To such mixtures the dyestuffs, 

 as indicated in table 7, are then added. 



Control tubes are prepared, the bouillon containing the same quanti- 

 ties of the dyestuffs, and are simply seeded with the staphylococcus. 

 These tubes demonstrate the^ possibility for growth in the dye-con- 

 taining medium. 



To all of these tubes which showed bacteriophagy a second implan- 

 tation of a concentrated suspension of staphylococci was made, yield- 



* A finely granular colloidal silver, yielding in water a very stable red pseudo- 

 solution. 



t These results suggest grave doubts upon the validity of the experiments 

 showing the so-called "oligodynamic" action of metals, of silver in particular. 

 If silver in its colloidal form is not active there is the more reason to suspect that 

 it may be inert when in its usual form. 



t We will see later that "secondary cultures" develop when the bacteriophage 

 used is not of a maximum potency. It is significant that in the presence of colloidal 

 sulfur secondary cultures are difficult to obtain, even though the bacteriophage 

 used does not prevent their formation in normal bouillon. 



