126 THE BACTERIOPHAGE AND ITS BEHAVIOR 



jected to bacteriophagy. This is true whether the process takes place 

 solely with the bacteria implanted when the number of corpuscles 

 inoculated is sufficiently great for all of the bacteria present to be 

 bacteriophaged at the beginning, or whether, because of the small 

 number of corpuscles present at first, the bacteria implanted have 

 had time to multiply before they are subjected to bacteriophagy. 

 Between these two extremes, — 1 corpuscle to 650 million bacteria, 

 and 10,000 million corpuscles (and even more with the Staphylo- 

 bacteriophage) to 1 bacterium,- — by varying the relative concentra- 

 tions of the two factors there is an infinite number of combinations 

 and of differing situations. But in every case the final number of 

 corpuscles is determined by the number of bacteria susceptible to 

 bacteriophagy, and, consequently, capable of serving for the multipli- 

 cation of the corpuscles. 



Influence of the conditions of the medium 



And yet, the statements made in the preceding section are true 

 only when the conditions of the medium are optimum for the process 

 of bacteriophagy. For example, if we vary the reaction of the medium 

 the final result of the multiplication of the corpuscles will vary, even 

 though in all cases bacteriophagy may be complete. The following 

 experiment clearly demonstrates this fact. 



A peptone water (peptone 25 grams, NaCl 5 grams, water 1000 cc.) 

 is rendered neutral to phenolphthalein. The medium is definitely 

 alkaline to litmus. After it has been distributed in 10 cc. amounts 

 into tubes, HCl is added in appropriate amounts to provide a series of 

 tubes having an increasing scale of acidity. All of the tubes are im- 

 planted with a concentrated suspension of Shiga bacilli to give a nor- 

 mal suspension, that is, 250 million per cubic centimeter. Then each 

 tube is inoculated with 0.001 cc. of the bacteriophage. After an 

 incubation period of 24 hours simple observation of the tubes indicates 

 varying degrees of turbidity, and appropriate counts indicate the 

 final number of corpuscles present in the individual tubes. In tabu- 

 lated form the results of such an experiment are as shown in table 12. 



Here are, for example, two strictly comparable experiments which 

 show that this is indeed the case. Inoculate 10 cc. of a suspension of 

 staphylococci containing 50 million bacteria per cubic centimeter 

 with but a single bacteriophage corpuscle. A count made after 3 

 days shows that although the medium is perfectly clear there are pres- 

 ent 81,000 million corpuscles. Inoculate a like suspension (20 cc. of 



