THE MECHANISM OF BACTERIOPHAGY 125 



lated at once with the bacteriophage multiphcation will take place 

 just as promptly and as vigorously as in an actively developing culture. 



Multiplication in relation to the number of bacteria bacteriophaged 



Working with B. dijsenteriae Shiga and with B. coli, Meuli^^- reached 

 the conclusion that the final ''lytic" titre is independent of the initial 

 titre. This deduction is true or false according to the conditions of 

 the experiment ; it all depends on the total number of bacteria available 

 and suitable for serving for the multiplication of the bacteriophage 

 corpuscles. If we combine in a medium a very few bacteria together 

 with a very small number of bacteriophage corpuscles, the corpuscles 

 which find a bacterium in their immediate vicinity readily available 

 will be relatively few and thus the opportunity for multiplication will 

 be restricted. Little by little, progressively, the number of corpuscles 

 will augment, but before the number becomes sufficiently great for 

 all of the bacteria, which meantime have had time to develop, to be 

 "parasitized," a culture equivalent to several hundreds of millions of 

 bacteria per cubic centimeter will have had time to mature. From 

 this it is apparent that when but very few corpuscles are inoculated 

 the initial titre of the bacteriophage is to a degree immaterial and 

 has no great effect upon the final titre. Incidentally this view of 

 Meuli is in some respects in accord with what I stated in the first 

 edition of my collected papers,^-^ namely; "In a word, whatever may 

 be the original titre of the suspension at the time when it is inoculated 

 with a limited number of bacteriophagous organisms the latter must 

 always operate on a suspension of about 650 million bacilli per cubic 

 centimeter, since in all cases the bacilli reproduce until they attain 

 this number." 



But MeuU has gone further, he has generalized, and his conclusions 

 are entirely false when the conditions are changed. If the medium 

 contains a small number of bacteria and a relatively large number of 

 bacteriophage corpuscles, the final titre depends upon the initial titre 

 in the sense that it varies but little, and solely in proportion to the 

 number of bacteria implanted. This is to be interpreted in this way: 

 each of the bacteria present at the moment of inoculation is in close 

 proximity to one of the corpuscles, since the latter are very numerous, 

 and all of the bacterial cells are parasitized and dissolved before they 

 have had time to multiply to any appreciable extent. 



To state the situation correctly, it may be said that the final number 

 of corpuscles depends upon the number of susceptible bacteria sub- 



