488 THE BACTERIOPHAGE AND ITS BEHAVIOR 



solution, in alcohol, and finally in distilled water. Fragments of the 

 nodules were placed on agar seeded with cultures of B. radicicola, and 

 they noted that after incubation each fragment occupied the centre of a 

 circle within which no growth had taken place. The action was spe- 

 cific; a fragment of a given nodule had an action only upon the strain 

 of B. radicicola derived from a plant of the same species. 



They subjected these nodules to extraction and made filtrates. These 

 filtrates contained races of the bacteriophage of high virulence, each 

 race being in general virulent for only those strains of B. radicicola 

 isolated from plants of the same species. But this specificity w^as not 

 quite absolute, for a bacteriophage isolated from the nodules of clover, 

 as also another race isolated from lupin, had a weak, but definite, viru- 

 lence for a strain of B. radicicola obtained from the nodules of the bean. 

 They were able to isolate races of the bacteriophage virulent for B. 

 radicicola from field soil, but did not find them in the earth of uncul- 

 tivated areas or forests. 



Like all other races of the bacteriophage, the corpuscles passed 

 through collodion membranes sufficiently permeable to allow the micel- 

 lae of serum globulin to pass. This explains the diffusion of the bac- 

 teriophage throughout the different parts of the plant, for these authors 

 have noted its presence in the stems, but not in the leaves. They 

 concluded that the fact that B. radicicola does not invade the entire 

 plant is due to the presence in the plant of a virulent race of the 

 bacteriophage. 



With plants, as with animals, antibacterial immunity is "exogenous;" 

 it is the bacteriophage protobe. This is a general fact, throughout 

 nature. 



RESUME 



The observations made in bacillary dysentery, in the typhoid and 

 paratyphoid fevers, and in avian typhosis, show that the behavior of 

 the intestinal bacteriophage toward a pathogenic bacterium which 

 becomes implanted in the intestinal tract varies; being determined, 

 (a) by the conditions found in the intestine, and (6) by the hereditary 

 characters of the bacteriophage and of the bacterium. 



The behavior of the bacteriophage may be summarized as follows: 

 All of the conditions of medium and of characters working to the 

 advantage of the bacteriophage, its virulence immediately increases 

 for the invading pathogenic bacterium; the result being the immediate 

 elimination of the bacterium before it can develop within the individual 

 and cause any disturbance. 



