Bacteriology. — ''Studies on the bacierlophagus of ü'Hp:kklle". 

 Bj J. W. Janzen and L. K. Woj.ff. (Communicated bj Prof. 

 C. Eykman). 



(Communicated at the meeting of May 27, 1922). 



IV. About the relation between bacteriophagus and resistant bacteria. 



d'Herelle tells us in his book that, when a weak bacteriophagus 

 is added to a thick emulsion of bacteria, the former will iiave 

 disappeared from the suspension after some time. 



Then he sajs that the bacteriophagus also seems to penetrate in(o 

 the bacteria, but that, now that the bacilli could not increase, the 

 bacterium resists the bacteriophagus, which is destrojed in vivo. 

 We have considered it important to studj this phenomon carefully 

 once more; for this we have used some tjphoidbacteriophagi, one 

 resistant and one not resistant tj^phoidstrain out of our collection. 



We have found that the disappearance of the bacteriophagus as 

 described by d'Herklle for thick emulsions also takes place in the 

 ordinary thin emulsions, this time not of normal but of resistant 

 bacilli. 



We have also found that old non resistant bacilli, which are not 

 being dissolved by the bacteriophagus in consequence of tlieir age, 

 do absorb the latter ; in this case however, the bacteriophagus only 

 increases when the bacteria multiplicate and so get young again. 



Some of the series of ex()eriments about this subject are as 

 follows : 



Series of experiments I. 



Resistant strain = T 20. Noii resistant strain = T Wi. 



Determination of the number of bacteriophagus germs by counting 

 the number of islands (on ag^rplate). 



Bacteriophagus Wi, 



Adding equal portions of bacteriophagus Wi to equally turbid 

 suspension in broth of T 20 and T Wi. 



Number of bacteriophagus germs per cM\ 



