BACTERIOLYSIS 



51 



tremely heavy it is found that the bouillon transplants made on 

 to agar after eighteen to twenty-four hours are always sterile. 

 The bacilli have been killed but not completely lysed. 



Experiment VIII 



After incubation for 8 hours all cultures appeared the same. 



The inhibitory force which interferes with lysis is due to the 

 accumulation of the soluble products resulting from the lytic 

 process, that is, to the activity of the ultramicroscopic bacterio- 

 phage itself. In this respect the action of the bacteriophage 

 is in accord with a phenomenon common to all cultivable micro- 

 organisms. 



Experiment IX. A bouillon suspension containing 250,000,000 bacilli 

 per cubic centimeter is inoculated with . 001 cc . of a culture of the bacterio- 

 phage. The next morning, or after fourteen hours, lysis is complete. A 

 count of the bacteriophage shows that there are 1,600,000,000 per cubic 

 centimeter. At this time a concentrated bacterial suspension is added 

 to the lysed suspension in such concentration that the titre amounts to 

 250,000,000 per cubic centimeter. Seven hours later the medium is again 

 limpid, and a count shows the presence of 2,100,000,000 ultramicrobes. 

 This second lysis completed, the bacterial content is again restored. This 

 time lysis is hardly accomplished in 48 hours, indeed, at this time the 

 bouillon is not quite clear. A count gives 2,400,000,000 ultramicrobes per 

 cubic centimeter. At this time, then, the medium contains in each cubic 

 centimeter the dissolved substance of 750,000,000 bacilli. The suspen- 

 sion is made up to a concentration of 250,000,000 once more (for the fourth 

 time). Eight hours later the culture has cleared somewhat but remains 

 decidedly cloudy. The count shows 2,600,000,000 ultramicrobes. Inocula- 

 tions upon agar and into broth remain sterile. 



It is plainly to be seen, therefore, that the more concentrated 

 the medium becomes in dissolved substances the more marked 

 becomes the inhibition and the less active the culture of the 

 bacteriophage. 



