THE BACTERIOPHAGE AND IMMUNITY 279 



bacterium for which the bacteriophage injected is virulent. 2 

 In hemorrhagic septicemia of the buffalo the optimum single 

 dose is a quarter of a cubic centimeter per hundred kilograms of 

 body weight. This question of dosage must be fixed by prelimi- 

 nary experiments for the other diseases. 3 



With disease once declared, the introduction into the patient 

 of the ultramicrobe virulent for the causative bacterium ought 

 to place the affected individual in a condition analogous to that 

 of the convalescent individual. The experiments in avian ty- 

 phosis and in human dysentery show in effect that the ingestion 

 or the injection of cultures of the bacteriophage exert a curative 

 action. 



The administration to a patient of an active culture of bac- 

 teriophage ought, as may be conceived, to be made at a time as 

 near as possible to the beginning of the disease. For this there 

 are two reasons. 



1. We have seen that the acquisition of virulence in the bac- 

 teriophage only represents one side of the question of recovery. 

 The bacterium may acquire a state of resistance such that the 

 action of the bacteriophage may be rendered inoperative. The 

 administration of a culture of the active bacteriophage should 

 have the more effect when the resistance of the bacterium is the 

 least. On the other hand, the acquisition of resistance is the 

 result of the conflict within the individual. Thus, the more 

 rapid the intervention the less likely will be the formation of 

 a resistant bacterial race. 



2. If there exists at the time of intervention organic lesions 

 incompatible with life the issue of the disease can not be other 

 than fatal whatever the power of the bacteriophage. 4 



2 It should be noted that here we are dealing with injection only. The 

 ingestion of cultures of the bacteriophage does not appear to be attended 

 by the development of an organic immunity. Ingestions can be repeated 

 without inconvenience, as I have demonstrated on myself. 



3 It should be emphasized that the cultures of the bacteriophage used in 

 immunization should be perfectly limpid; that is to say, the lysis ought 

 to be complete. Filtration through a bougie is essential, for the reason 

 which we have seen. If necessary, filtration may be replaced by heating 

 at 58C., but filtration is to be preferred. 



4 The cases recently described by Beckerich and Hauduroy, which 

 were mentioned in the note at the end of the preceding chapter, corroborate 



