BACTERIOPHAGE AS AN ANTIGEN 383 



for the bacterium injected. I have shown^^^ that it is the exception 

 for this experiment to give the result claimed for it by Bordet and 

 Ciuca, but by modifying the conditions under which it is done only 

 to the extent of having the animal ingest, a few hours before the intra- 

 peritoneal injection, a suspension of bacteriophage virulent for the 

 bacterium injected, the experiment uniformly becomes successful. 

 This proves that the bacteriophage isolated comes from the intestine, 

 the passage into the peritoneum through the intestinal wall being in- 

 duced by the irritation caused by the presence of the bacteria in the 

 body cavity. Although lending but scant support to Bordet's hypoth- 

 esis of the origin of the bacteriophage, this experiment does show one 

 thing very definitely, namely, that a resorption of bacteriophage pro- 

 tobes through the intestinal wall can occur. The fact that the cor- 

 puscles can and do pass into the body has been confirmed by many 

 investigators, whose contributions to the subject will be presented in 

 the discussion to follow. 



When bacteriophage protobes have penetrated into the tissues what 

 is their fate? 



The experiments of Appelmans^- already mentioned have shown us 

 that bacteriophage protobes behave like bacterial spores; they become 

 concentrated in the spleen where they persist for some time after 

 they have disappeared from the other tissues. This strongly suggests 

 that they must be carried there, or retained there, by the phagocytes. 



Bruynoghe and Maisin^-^ have presented direct evidence that the 

 bacteriophage protobes are phagocytized. They carefully mixed a 

 trace of a bacteriophage suspension with 2 cc. of fresh sterile pus. 

 The number of corpuscles present was determined immediately and 

 again after incubation for 24 hours at 37°C. Comparison of the two 

 titrations showed that a very considerable diminution occurred, which, 

 according to the experiment, represented a reduction by some hundreds 

 or thousands of times. 



It thus appears that the bacteriophage protobes behave in the body 

 like saprophytic bacteria. But the substance of the protobes 

 is protein in nature, and these proteins must function as antigens. 

 That this is true is amply demonstrated by the data presented in the 

 following section. 



2. ANTIBACTERIOPHAGIC SERA 



Bordet and Ciuca^^ gave rabbits several injections of a suspension 

 of Coli-bacteriophage. The animals were bled a few days after the 



