482 THE BACTERIOPHAGE AND ITS BEHAVIOR 



one case, in the course of the afternoon in the three others, blood cul- 

 tures were negative. In three cases a bacteriophage active for B. gal- 

 linarum was found in the blood. The blood which was ultrasterile 

 was that of the chicken whose condition was the best at this time and 

 which had shown no pathogenic bacilli in the intestinal tract in the 

 morning. The presence of the bacteriophage in the blood is extremely 

 transitory. 



On the morning of the third day the animals appeared normal, they 

 drank a great deal, ate some grain, and the diarrhea was less profuse. 

 Examination of the feces showed : 



B. gallinarum absent in the four cases. 



Intestinal bacteriophage active for B. coli + + + (4 cases), for B. 

 gallinarum + + + (3 cases) + + + + (1 case). Blood cultures were 

 negative: no bacilli, no bacteriophage. 



On the fourth day the animals were practically normal. 



In the four chickens which recovered the intestinal bacteriophage 

 remained active for B. gallinarum for a very long time. After three 

 months it showed the same degree of activity as at the time of recovery. 

 In one of them, in which it was possible to make an examination after 

 five months, it was still as active as at first. We will see, from experi- 

 mental observations that this persistence of virulence depends solely 

 upon the fact that the pathogenic bacillus, distributed in profusion in 

 the exterior environment, is frequently ingested by the animal and this 

 maintains the virulence of the intestinal bacteriophage since it is able 

 to grow at its expense. 



The feces of about one hundred chickens which had died of avian 

 typhosis were examined. In no case was there a bacteriophage active 

 for B. gallinarum or for any of the bacillary agents of the paratyphoses. 

 Nevertheless the bacteriophage had been present for it could be dis- 

 closed (91 times in 97 examinations) because of the activity shown for 

 one or several species of the colon-typhoid-dysentery group. One sees 

 clearly, then, that the lack of defense is not due to the absence of the 

 bacteriophage, but solely to the fact that the intestinal bacteriophage 

 remained passive because it failed to acquire a virulence for the path- 

 ogenic bacillus. 



To summarize : as in dysentery and in typhoid fever in human beings, 

 the acquisition of virulence by the intestinal bacteriophage for the 

 pathogenic bacterium is the sine qua nan of recovery. 



Kramer^ ^^ also, has found that the bacteriophage plays an important 

 role in immunity to avian typhosis. We will consider his contribution 

 to the subject in more detail a little later. 



