CHAPTER I 



Bacteriophagy in a Fluid Medium 



1. isolation of the bacteriophagous principle 



Ubiquity of the bacteriophage 



The description of the fundamental experiment, as presented in the 

 early pages of the Introduction, demonstrates that the phenomenon 

 of bacteriophagy consists essentially in the dissolution of the bacterial 

 cell.* This is accomplished through the action of a "principle" which 

 passes through porcelain filters, and even, as we shall see, through 

 ultrafilters whose pores are large enough to permit the passage of par- 

 ticles with a diameter as great as 30 miUicrons.f 



Quite naturally the first question to arise is that of the isolation of 

 this dissolving principle, that is, how can it be obtained in a pure 

 state, in the bacteriological sense of the word. Where is it to be found 

 in nature? What types of material must be examined to obtain it? 



It is everywhere present, one might say. Up to the present time 

 it has been shown to be present not only in the intestinal contents 

 of the normal man and of healthy anunals (d'Herelle^^'')| but par- 

 ticularly in those who are convalescent from a bacterial infection 

 {d'B.eTe\\e^^°'^^*''^^"), in the urine of these convalescents (d'Herelle^^"), 

 in theu' blood (d'Herelle^^^), in pus (d'Herelle^-^, in river water 

 (Dumas' ^^), and in cultivated soil (Dumas^^^). Being, in fact, a con- 

 stant inhabitant of the intestinal tract it may be encountered in every- 

 thing which may be contaminated by fecal material. 



Its constant presence in the intestine suggests indeed, a priori, the 

 thought that certain bacterial strains may occasionally be found "con- 

 taminated" by a bacteriophage, and in fact, Otto and Munter^^^ j^^ve 



* The word "cell" is used here simply because it is sanctioned by usage. As a 

 matter of fact, it is very doubtful if a bacterium can be formed of a cell, in the 

 strict sense of the word. This question is discussed in the next to the last chapter 

 of "Immunity in Natural Infectious Disease." 



t A millicron is one one-millionth of a millimeter, or one one-thousandth of a 

 micron, i.e., Iju/z. 



J Only the original papers are here cited. In a later chapter dealing in greater 

 detail with the distribution of the bacteriophage we will review more extensively 

 the findings of those who have investigated this question. 



37 



