44 THE BACTERIOPHAGE AND ITS BEHAVIOR 



alkalinity that provides optimum conditions it becomes apparent at 

 once that the conditions obtaining in one experiment are optimum 

 conditions only for the bacterial species and the particular race of 

 bacteriophage with which the experiment is performed. If another 

 species of bacteria and a bacteriophage derived from another source 

 are utihzed the best conditions for effecting the phenomenon may be 

 quite different from those of the first experiment. 



Situations analogous to this will be observed repeatedly in the course 

 of this study, and the reason for such a lack of fixed relationships is very 

 obvious. Although in physics, or in chemistry, it is always possible 

 to definitely fix the conditions of an experiment, to record these condi- 

 tions by giving them invariable numerical expression, and to make the 

 experiment entirely without regard to the past history of the chemical 

 substances entering into the reaction, this is not possible in biology. 

 Here, the past, the inheritance of the beings involved, constitutes a 

 factor of prime importance. Moreover, this factor is always difficult, 

 often impossible, to evaluate in advance. This is why two experi- 

 ments in bacteriophagy, carried out under identical conditions, may 

 yield different results, simply because in the two experiments the 

 bacteria are of different species, or simply of different strains. Bacteri- 

 ophagy is a disease of bacteria, and the aphorism, so true, "there 

 are not diseases, there are patients," meaning that a single disease 

 may have varied manifestations according to the individual affected, is 

 just as true whether the patient be a man, or whether it be a bacterium. 



In the last analysis, it is of course true, that disease represents the 

 sum total of a series of purely chemical reactions, but whereas in 

 chemistry a reaction can be predicted in its most minute details be- 

 cause of restricted conditions, all determinable in advance, in biology 

 generally, and certainly in the case with which we are particularly 

 concerned, the number of factors is so great, the majority of these 

 factors being absolutely indeterminable, that it is impossible to predict 

 the optimal conditions for a reaction. Only the general nature of the 

 reaction can be foretold. 



This concept must always be held in mind throughout the study of 

 the phenomena caused by the bacteriophage. A great many authors 

 have neglected these fundamental principles, with the result that many 

 conflicting reports, with their attendant arguments, have appeared, 

 each author assuming that he could generahze from his individual 

 results. As a matter of fact, these basic facts are all-important, and 

 generalization is particularly hazardous. 



