BACTERIOLYSIS 49 



soluble substances resulting from the vital activity of the bac- 

 teria diffuse into the agar and these substances constitute an 

 actual specific antiseptic which limits the culture. The medium 

 is " vaccinated" around the colony. The deeper the agar layer, 

 or the farther the colonies are separated, the greater the volume 

 of the substratum capable of diluting this antiseptic substance, and 

 the larger will be the colony. The situation is precisely the same 

 with the bacteriophage; the more scattered the colonies and the 

 deeper the substratum, the greater the diameter. Direct ex- 

 perimentation proves the correctness of this interpretation, and 

 that the soluble substances elaborated during the lytic process, 

 substances resulting from the vital activity of the bacteriophage, 

 inhibit the vital processes, delay growth, and prevent the ac- 

 complishment of total lysis. 



EFFECT OF THE CONCENTRATION OF BACTERIA IN THE MEDIUM; 

 INHIBITORY EFFECTS OF THE PRODUCTS OF LYSIS 



In all of the experiments involving the action of the bacterio- 

 phage in a liquid medium which we have up to the present con- 

 sidered the bacterial suspension has contained approximately 

 250,000,000 organisms per cubic centimeter. 



What occurs if the concentration of suspended bacilli is varied 

 between 50 and 500 millions? The end result will always be 

 the same a complete lysis and even the time required for this 

 lysis will not greatly vary for the inoculation of a given quantity 

 of the bacteriophagous culture, such is the rapidity of develop- 

 ment of these organisms. Let us consider the two extreme cases. 



Experiment VII (A.) The inoculation with the bacteriophage is 

 massive, that is, 0.02 cc. In such a case the difference in time is most 

 marked. 



Number of bacilli Lysis is complete 



per cc. in 



50,000,000 4| hours 



100,000,000 4 hours 



200,000,000 5 hours 



250,000,000 5 hours 



300,000,000 5 hours 



400,000,000 6 hours 



500,000,000 8 hours 



(B.) The inoculation with the bacteriophage is very weak, in the follow- 

 ing experiment, 0.00,000,1 cc. 



