HYPOTHESES CONCERNING NATURE OF BACTERIOPHAGE 323 



autolysis is once completed ought to effect the phenomenon of bacteri- 

 ophagy. But experiment shows that this liquid is absolutely inert. 

 Bouillon seeded with the homologous staphylococcus yields, despite the 

 addition of any quantity of the autolysis fluid, a normal culture, com- 

 parable in all respects to a control culture made by implanting the 

 staphylococcus into plain bouillon. A suspension of the staphylococcus 

 to which the autolysis fluid, filtered or unfiltered, is added in any quan- 

 tity whatsoever, behaves just as does a normal control suspension. 

 Spread over an agar surface it gives a normal culture, never showing 

 any signs of the plaques characteristic of bacteriophagy. 



These experiments show by a direct method that the bacteriophage 

 principle is not an autolysin and that it is not present in the normal 

 bacterium. 



But, you may say, no doubt this is true, it may very well be that bac- 

 teriophagy is not a "normal autolysis," nevertheless bacteriophagy may 

 occur as the result of some phenomenon in which autolysins intervene. 

 Indeed! This is an entirely different affair, and is an hypothesis which 

 we are quite willing to consider. But, however that may be, it is cer- 

 tain that the principle which "provokes" bacteriophagy is not a con- 

 stituent of the normal bacterium; the experiments recorded above show 

 this conclusively. 



Very recently Gildemeister and Hermann thought that they had, at 

 last, disclosed a fact supporting the idea that the bacteriophage is 

 produced by the bacterium. They isolated a strain of B. colt which 

 was "lysogenic;" whose filtrate caused an intense bacteriophagy of 

 B. dysenteriae. But this took place only when they cultivated the 

 colon bacillus at a temperature above 15°C. In cultivations below this 

 temperature they could not demonstrate the lytic principle. And so, 

 they reasoned, if we make a series of cultures at 10°C. we will lose the 

 strain of bacteriophage and then if we subsequently cultivate it at 37°C. 

 the cultures should no longer be lysogenic. But, they found, on the 

 contrary, that under these conditions the later cultures were perfectly 

 lysogenic. From these observations they concluded that the bacterio- 

 phage is a product of bacterial metabolism, produced only under 

 restricted conditions, insofar as temperature is concerned, between 15° 

 and 37°C. 



The experiments of Gildemeister are always very well executed, but 

 he should, nevertheless, employ methods beyond criticism. The method 

 of isolating the bacteriophage which he employed is defective, and has 

 frequently led to erroneous conclusions. To determine whether his 



