CHAPTER I 



The Behavior of the Bacteriophage Toward Different Agents 



1. the physical state of the bacteriophage 



I will not revert here to the question of the corpuscular nature of the 

 bacteriophage, since this subject has been discussed at length in Part I. 

 Moreover, the demonstration that I have given has not been disputed. 

 Everyone has accepted this fact, whatever their concept as to the inti- 

 mate nature of the corpuscle itself.* 



A suspension containing more than 10,000 million corpuscles per 

 cubic centimeter is perfectly limpid, not only after it has been passed 

 through a filter candle but even immediately after bacteriophagy, 

 provided dissolution is brought about through the action of a bacterio- 

 phage of maximum virulence. 



When a ray of light is passed through a perfectly clear suspension 

 of the bacteriophage the Tyndall phenomenon may be observed. 



At first I believed that the fine granules, appearing as brilliant points 

 when a bacteriophage suspension is observed under the dark-field, must 

 be the bacteriophage corpuscles. Exceptions were taken to this view, 

 and apparently quite correctly, for further study indicates that these 

 granules are certainly derived from the dissolved bacteria. If a sus- 

 pension is allowed to sediment for a few weeks, the supernatant fiuid 

 becomes free of granules capable of detection by dark-field examination, 

 despite the fact that this fluid contains an abundance of bacteriophage 

 corpuscles. 



Additional evidence is afforded by the repeated examination of a 

 bacterial suspension which has undergone bacteriophagy, for it is found 

 that although these brilliant points are very abundant immediately 

 after the dissolution is finished, they diminish rapidly. After three 

 days only one or two can be found in each field. Thus, they are most 



* Doerr alone, as I have already stated, has hesitated to commit himself. He 

 has, however, shown that the bacteriophage principle does not pass through 

 tight collodion membranes. If a body does not pass through such a membrane it 

 is obviously because it is not in solution, but is in suspension, for it must be in 

 either one or the other of these states. And if it is found as a suspension it is 

 formed of corpuscles. 



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