NATURE OP BACTERIOPHAGE 339 



passages are continued, show the distinctive characters of bacteriophage 

 h, in particular, its polyvirulence. 



This experiment, which offers no chance for misinterpretation, which 

 yields a result so absolutely clear-cut, for it is impossible to confuse two 

 characters as distinct as univirulence and multivirulence, demonstrates 

 that the bacteriophage is an autonomous being, independent of the bac- 

 terium at the expense of which it multiplies. 



As a matter of fact, bacteriophage v attacks strain V only. If it is 

 a product derived from the metabolism of the bacterium it must be 

 elaborated by the V strain of Staphylococcus albus and its character 

 of specificity depends upon the staphylococcus which produces it. If 

 this conclusion is not admitted the alternative is to recognize that the 

 properties of the bacteriophage are independent of the bacterium which 

 undergoes its action, and this enforces acceptance of the autonomous 

 nature of the bacteriophage. If, on the contrary, one considers the 

 bacteriophage to be a product of bacterial metaboHsm and if this con- 

 ception is valid, all of the bacteriophage corpuscles derived from the 

 metabolism of staphylococcus V should present the same characters, 

 especially that of being univirulent. Bacteriophage h, because of the 

 serial passages, should have lost its character of multivirulence. But 

 the result is precisely the opposite. After any number whatever of 

 such passages it remains multivirulent. From this, therefore, it is 

 certain that the bacteriophage possesses its own characters; and but 

 one deduction can be drawn, namely, that the bacteriophage is an 

 autonomous being, independent of the bacterium at whose expense it 

 multipHes. 



VIII. I have repeated the preceding experiment in a somewhat differ- 

 ent way. To begin with, bacteriophagy of a suspension of staphylococ- 

 cus V was induced by the inoculation of a suspension of bacteriophage 

 h, previously heated to 60°C. After a complete dissolution the limpid 

 suspension was returned to the incubator at a temperature of 41°C. 

 After 3 days a secondary culture developed. For the past two years 

 this mixed culture has been carried on by transfers made about once a 

 month. After 24 subcultures a filtrate was made from a seeding of the 

 mixed culture of the last transfer. This filtrate contained the bacterio- 

 phage, and this bacteriophage had all of the characters of bacteriophage 

 h. It was multivirulent. 



A mixed culture, — Bacteriophage «;-Staphylococcus F, — ^has been 

 maintained for about four years, having undergone many transfers 

 (from 30 to 40). It still contains a strictly monovirulent bacterio- 

 phage, attacking staphylococcus V only. 



