THE BACTERIOPHAGE IN DISEASE 213 



virulent for B. gallinarum (+ + ++). 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 through- 

 out 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. gallinarum 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 bacteriophagous 

 ultramicrobe 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 re- 

 ceived per os, on some bread, a single dose of 2 cc. of a bouillon 

 culture of B. gallinarum. Three days after the infecting meal 

 diarrhea appeared and they died two and three days later, after 

 having shown all of the symptoms of the natural disease. Ne- 

 cropsy showed the presence of the same lesions. Cultures of 

 the blood gave pure cultures of the pathogenic bacillus, which 

 was likewise found in abundance in the intestinal contents. 



Chickens nos. 1, 3, and 4, which had resisted repeated inges- 

 tions of B. gallinarum culture without showing the least incon- 

 venience, were therefore immunized; the first as a result of the 

 ingestion of a bacteriophage 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 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. 



In all of these experiments the infections have been made with 

 bouillon cultures of B. gallinarum prepared directly from the 



