82 THE BACTEEIOPHAGE AND ITS BEHAVIOR 



2. THE BACTERIOPHAGE CORPUSCLE 



The hypothesis which I have formulated in answer to the above ques- 

 tions is easy to verify. The experiment described in the preceding 

 section showed that bacteriophagy occurred in the bacillary suspension 

 containing 10~^*' cc. of bacteriophage filtrate, while the phenomenon 

 failed to take place in the suspension with the next higher dilution, 

 10-11. 



If the bacteriophage exists in corpuscles this result is at once 

 explained. What happens would then be exactly of the same nature as 

 that which takes place when tubes of sterile bouillon are planted with 

 serial dilutions, ever more and more dilute, of a bacterial culture. The 

 tube of bouillon which receives one drop of a sufficiently high dilution 

 will be implanted with but a single bacterium, but it will yield, after 

 incubation, a culture as abundant as that of another tube seeded with 

 several million of the same bacteria. On the other hand, the tube which 

 receives one drop of the next dilution, will not yield a culture, for the 

 drop introduced did not contain even a single bacterium. Either there 

 will be growth, or there will not be growth. And, in the same way, 

 bacteriophagy either occurs, or it does not occur. There are no inter- 

 mediate gradations. Let us find out if this is the case; if experiment 

 confirms theory. 



Prepare again the same series of dilutions, in tens, as those described 

 in the experiment of the preceding section, employing the same bacterio- 

 phage filtrate, but instead of making the successive dilutions in suspen- 

 sions of B. dysenteriae, make them in sterile bouillon. The procedure 

 consists simply in introducing 1 cc. of bacteriophage filtrate into 9 

 cc. of sterile bouillon, removing 1 cc. of this first dilution and placing it 

 into a second tube containing 9 cc, then 1 cc. of this second dilution 

 carried over into the next tube, and so on up to the tenth dilution. This 

 last tube will then contain 10 cc. of bouillon in which there will be 10"^ 

 cc. of bacteriophage filtrate, and each cubic centimeter of this tenth 

 dilution will therefore contain lO-^" cc. of the filtrate. 



Suspend in a flask containing 90 cc. of sterile bouillon some B. dysen- 

 teriae removed from a young agar slant, in such a way that each cubic 

 centimeter of the medium will contain about 100 million bacilli. Dis- 

 tribute this 90 cc. of bacterial suspension among 10 tubes, 9 cc. to each. 

 To each tube add 1 cc. of the bacteriophage principle previously diluted 

 to 10"i°. We now have 10 tubes of suspension, and in each of them an 

 added 1 cc. of a 10-i° dilution of the bacteriophage filtrate. Place the 

 10 tubes in the incubator at 37°C. 



