86 THE BACTERIOPHAGE AND ITS BEHAVIOR 



extent of the dilution of the bacteriophage principle which is inoculated 

 into the suspension. In other words, with a Staphylo-bacteriophage 

 still causing bacteriophagy in the tube diluted to 10"^^ (the dilutions 

 being made by tens in volumes of 10 cc.) and not causing bacteriophagy 

 in the tube with 10~^- dilution, it is not because this last tube has a dilu- 

 tion of 10~^2 that bacteriophagy does not result, but simply because it 

 has not received a single bacteriophage corpuscle. 



To further emphasize this point, let us take, as did Gratia and 

 deKruif"" a liter of a staphylococcus suspension* and let us inoculate 

 it with 1 cc. of a 10^^*' dilution of Staphylo-bacteriophage. The dilu- 

 tion of the principle in this liter of suspension will be 10~^^, yet bacterio- 

 phagy occurs. The reason is plain. We know that 1 cc, of the 10~^° 

 dilution causes bacteriophagy when added to 9 cc. of bacterial suspen- 

 sion, clearly showing that it contains at least one bacteriophage cor- 

 puscle. And it makes no difference whether this corpuscle is inoculated 

 into 10 cc. or into 10 liters of suspension. The result is the same, the 

 principle multiphes and causes bacteriophagy. 



In brief, then, the concentration of the bacteriophage principle in a 

 suspension where bacteriophagy is to take place is of little importance. 

 For the phenomenon to occur the necessary and sufficient condition is 

 that at least one bacteriophage corpuscle be introduced into the suspen- 

 sion of organisms. 



In conclusion, let me repeat just once more, that to be conclusively 

 demonstrable, these experiments must be made with a very active 

 bacteriophage principle, that is, with one capable of causing a complete 

 and permanent dissolution of the susceptible bacterium when 250 mil- 

 Hon bacteria per cubic centimeter are present.! 



* These authors performed the experiment with a Coli-bacteriophage. I have 

 repeated it with a Staphylo-bacteriophage, and the results have been identical 

 in principle. They could not be otherwise. These authors stated that their 

 experiment was open to several interpretations. This rather vague conclusion 

 appears to have satisfied them, for the suggested interpretations have not yet 

 appeared. As a matter of fact but a single interpretation is possible. The 

 bacteriophage exists in the form of corpuscles. The experiment of Gratia agrees 

 with experiments that I had published on several occasions, and this is all that 

 Gratia could have said. 



t In studying the phenomena of the resistance of the bacteria to the bacterio- 

 phage we will see the reasons why the experiment demonstrating the corpuscular 

 form must be carried out with an extremely active bacteriophage principle. 



