336 



THE BACTERIOPHAGE AND ITS BEHAVIOR 



were sure that I had sent them six different races. As I had been 

 accustomed to give a different number to each race I repHed to them in 

 the ajffirmative, although I could not verify this statement from my 

 experimental protocols which I was unable to consult since I was at the 

 University of Leiden and my records of these races were in Paris. 



They found, as a matter of fact, that after these six races of the bac- 

 teriophage had been subjected to serial passages with a single strain of 

 B. typhosus, the virulences were as shown in table 32. 



From these results these races could clearly be divided into two groups 

 one comprising races 1 and 2, the other races 3, 4, 5, and 6. This indi- 

 cated that there must have been some mistake on my part. And they 

 had good reasons for such a suspicion. Some time later, being in Paris, 

 I consulted my laboratory protocols, and I found that these races of the 



bacteriophage had been isolated before I adopted the notation later 

 used,^and I had designated by the different numbers a bacteriophage of a 

 single race which had been through passages with different strains. 

 In reahty, races 1 and 2 were derived from a convalescent from typhoid 

 fever, while races 3, 4, 5, and 6 were all obtained from another case. 



The distinguishing characters of a race of the bacteriophage are so 

 marked, even after repeated passages with different strains of a 

 bacterium, or even after passages with bacteria of different species, that 

 it is possible to distinguish them from all other races. This would not be 

 the case if the bacteriophage were a product of the bacterium, for then 

 it could not retain its individuality in this way. 



V. Maitland performed an experiment which is essentially the reverse 

 of that of Janzen and Wolff. He isolated a bacteriophage which was 

 virulent for both B. paratyphosus B and B. dysenteriae. This, he car- 

 ried through a series of passages, on the one hand, with B. paratyphosus 

 B, and on the other, with B. dysenteriae. He found that the bacteri- 

 ophage remained the same, whether it was maintained at the expense of 

 the one or the other of these bacteria. 



