CHAPTER III 



Immunization by Means of the Bacteriophage 



Immunization against Avian Typhosis. Immunization against Barbone* 

 Immunization against Dysentery. Conclusions. 



The single test scientifically acceptable for a theory of im- 

 munity can be furnished only by the reproduction of this im- 

 munity in an animal naturally susceptible. That is, in placing 

 this animal by experiment in the condition to which immunity 

 is attributed. 



A strain of the bacteriophage active for a given bacterium can 

 be isolated and cultivated in vitro indefinitely at the expense of 

 this bacterium, thus maintaining its virulence. In this way any 

 desired amount of culture can be obtained. 



If the theory of immunity by the bacteriophage which we have 

 deduced from the investigations made on natural disease is 

 correct we should be able at will to reproduce all the phenomena 

 leading to recovery, provided there do not exist at the time of 

 intervention organic lesions incompatible with life. We should 

 likewise be able to place the exposed individual in the same re- 

 fractory state enjoyed by the person who has passed through the 

 epidemic period unaffected. It is for this reason that up to the 

 present time I have confined myself almost entirely to a study of 

 the role of the bacteriophage in animals, since these alone permit 

 of experimental confirmation. 



water should contain the greatest possible number of bacteriophagous 

 ultramicrobes virulent for the agents of contagious diseases. It is certain 

 that to obtain such waters, containing at once the greatest possible number 

 of virulent ultramicrobes and the smallest possible number of bacteria it 

 is necessary to use filtered river water and not stored waters. As potable 

 waters the first are at the same time superior, from both the hygienic 

 and economic points of view. 



Attention may be called to the fact that in certain cases a search for 

 a bacteriophage virulent for a given bacterium may be of some significance 

 in hydrological investigations. 



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