510 THE BACTERIOPHAGE AND ITS BEHAVIOR 



But while many of these questions are of the greatest theoretical 

 interest, I must add that I am absolutely indifferent toward the study 

 of such fictitious immunities, developed for fictitious experimental 

 diseases. The only thing that interests me in this connection is the 

 immunity obtained against the natural disease. Upon several oc- 

 casions I have expressed my ideas on this subject.^21,349 



2. IMMUNIZATION AGAINST AVIAN TYPHOSIS 



Immunization experiments made in a region where the epizootic 

 was present, as was true in the case of avian typhosis, presented an 

 especial difficulty, or rather, a complication. It has been mentioned 

 that aside from the typical typhosis, due to B. gallinarum, there are 

 several varieties of paratyphoses, each caused by a particular species 

 of bacterium. The differences which these bacterial species present 

 from the biochemical and agglutinative points of view and which serve 

 to differentiate them are of no particular significance from the point 

 of view of this study. In so far as action of the bacteriophage is 

 concerned for each of these, a race of bacteriophage having an extreme 

 virulence (+ + ++) for B. gallinarum possesses the same activity for 

 all the French and American strains as well as for B. jeffersonii. The 

 activity is less pronounced for B. pullorum A, still less for B. pullorum 

 B, and is lacking for B. pfaffi and for B. rettgeri. With such a race 

 of bacteriophage the reactions are: B. gallinarum + + + +, B. jef- 

 fersonii + + + + , B. pullorum A ++, B. pullorum B -]-, B. pfaffi 0, 

 and B. rettgeri 0. Inversely, a race of bacteriophage secured from 

 fowls resistant to paratyphosis due to B. pfaffi (focus at Trainel, Aube) 

 had the following virulences: B. gallinarum 0, B. jeffersonii 0, B. pul- 

 lorum A 0, B. pullorum B -\-, B. pfaffi + + + +, and B. rettgeri 0. 



The immunization experiments thus become singularly complicated, 

 particularly since both typhosis and the paratyphoses may be found 

 in the same areas, as is also true for human enteric infections. In 

 routine practise the solution is simple; it is sufficient to immunize the 

 poultry with a mixture of different races of the bacteriophage active 

 against the diverse pathogens, the causes of typhosis and the para- 

 typhoses. In the prehminary investigations this was not possible, 

 for the differences between the different diseases had not been recog- 

 nized when I first undertook this study. The different bacilli, the 

 agents of the paratyphoses, had been studied in the United States but 

 their simultaneous presence in foci of typhosis had not been noted. 

 And in so far as B. pfaffi is concerned, discovered by Pfaff in an epi- 



