494 THE BACTERIOPHAGE AND ITS BEHAVIOR 



In the course of the preceding experiment chickens Nos. 3 and 4 were 

 placed in contact with chicken No. 1. They all ate and drank from the 

 same containers, the more so since they were changed about in the pens 

 in such a manner as to simulate conditions of life analogous to those of 

 the chicken-yard. Two days after the first contact, in the case of 

 chicken No. 3, three days after with chicken No. 4, their excreta con- 

 tained a bacteriophage very virulent for B. gallinarwn (+ + + + ). 

 From this time on they each received each day for twenty-one days, 2 

 cc. of a bouillon culture of B. gallinarum. At no time did they appear 

 sick. The intestinal bacteriophage remained active for the bacillus 

 throughout the entire period of the administration of the pathogenic 

 bacillus, and even longer — seven days in No. 4 and ten days in No. 3. 

 The intestinal bacteriophage did not then disappear, for as in the case of 

 chickens Nos. 1 and 2, it remained active for one or several members of 

 the colon-typhoid-dysentery group. But the virulence for B. galli- 

 narum did not persist when the ingestion of cultures of this last bacillus 

 was stopped. The experiment with chickens Nos. 3 and 4 shows clearly 

 that the bacteriophage protobe is infectious in exactly the same sense as 

 is the pathogenic bacillus itself, since these birds were "contaminated" 

 by contact with chicken No. 1. 



Chickens Nos. 5 and 6, which had not been in contact with the 

 other chickens, and which on repeated examinations were shown to be 

 free of a bacteriophage active for B. gallinarum, each received per os, 

 on some bread, a single dose of 2 cc. of a bouillon culture of B. galli- 

 narum. Three days after the infecting meal diarrhea appeared and 

 they died two and three days later, after having shown all of the symp- 

 toms of the natural disease. Necropsy showed the presence of the same 

 lesions. Cultures of the blood gave pure cultures of the pathognic 

 bacillus, which was likewise found in abundance in the intestinal 

 contents. 



Chickens Nos. 1, 3, and 4, which had resisted repeated ingestions of 

 B. gallinarum culture without showing the least inconvenience, were 

 therefore immunized; the first as a result of the ingestion of a bacterio- 

 phage active for the pathogenic bacterium, the two others by simple 

 association with the first. 



About one month after the virulence of the bacteriophage for B. 

 gallinarum had disappeared in chickens Nos. 1, 2, 3, and 4 each of them 

 was given on each of the three days 2 cc. of a culture of the bacillus. 

 In all the intestinal bacteriophage showed a new virulence for the 

 pathogenic organism. None of them showed the slightest trouble. 



