NATURE OF BACTERIOPHAGE 341 



All of these experiments contribute in showing that the "substance" 

 of the bacteriophage corpuscle is different from the "substance" of the 

 bacterium at whose expense it multiplies ; that the characters of the cor- 

 puscle belong to it itself and are not determined by the characters of the 

 bacteria which undergo its action. The bacteriophage corpuscle is, 

 therefore, an autonomous being. 



4. THE POWER OF ASSIMILATION OF THE BACTERIOPHAGE CORPUSCLE 



The bacteriophage multiplies during the course of its action. We 

 have seen that with highly potent races a single corpuscle inoculated into 

 10 cc. of a suspension of a susceptible bacterium will yield, when bacter- 

 iophagy is terminated, as many as 100,000 millions per cubic centimeter. 

 The solitary one introduced into the 10 cc. of medium will have become 

 a trillion; the suspension of bacterial cells will have become a suspension 

 of bacteriophage corpuscles. The "mass" of bacteriophage substance 

 has, then, increased from 1 to 1 trillion. 



Proof has been adduced that the bacteriophage is not a product of 

 bacterial metabolism; that the bacteriophage corpuscle is an autono- 

 mous being. And an autonomous being whose mass increases neces- 

 sarily utilizes the substances found in its environment, transforming 

 these heterologous substances into its own peculiar substance. Experi- 

 ment shows that the bacteriophage multiplies at the expense of bacteria, 

 that it must transform "bacterium substance" into "bacteriophage 

 substance," and this can only mean that the bacteriophage corpuscle is 

 endowed with the power of assimilating a heterologous medium. 



5. THE POWER OF ADAPTATION OF THE BACTERIOPHAGE CORPUSCLE 



I. We know that the vigor with which a bacteriophage corpuscle will 

 attack a given bacterium is capable, according to the conditions of the 

 experiment, of being enhanced or of being diminished. As a matter of 

 fact, at the present time, this fact is universally accepted. 



May one say, with Seiffert,"^ that it is not really an exaltation or an 

 attenuation in the virulence of the corpuscle for the bacterium, but 



This experiment of Prausnitz is open to criticism, for one may object that if 

 one saturates a serum which is both antitoxic and antibacterial with young bac- 

 teria the antibacterial properties will disappear while the antitoxic properties 

 will remain, nevertheless, a toxin is certainly a bacterial product. 



Prausnitz is correct in his deductions, but his experiment is not beyond criti- 

 cism. Those of Bordet and Ciuca, on the contrary, are not open to attack. 



