PROPERTIES OF THE BACTERIOPHAGE 307 



multivirulent the different virulences exhibited at the same time are not 

 equally sensitive. Exposed to a given agent some of the virulences 

 disappear, while others are retained (Reichert^^") , and recent investiga- 

 tions provide us with the reason for this diversity. 



We can reveal the presence of the bacteriophage only through mani- 

 festations of its virulence. By the means now available the loss of 

 virulence and destruction manifest themselves in the same manner, 

 that is, by the lack of bacteriophagy. And yet, many experiments 

 indicate that before an actual destruction occurs there is an attenuation 

 of the bacteriophage or its virulences. When exposed to the action of 

 many different physical or chemical agents, attenuation begins and 

 progressively increases with the exposure so that with races having 

 multiple virulences, the virulences disappear in the inverse order 

 of their intensity, the weakest ones go first, the stronger ones next, and 

 the chief and most intense one last. Up to the time when this chief 

 one has disappeared interruption of the contact with the harmful agent 

 leaves it still possible to restore the activity by the method of serial 

 passages at the expense of susceptible bacteria. Working with Pozerski, 

 I was the first to show this fact as it obtains in rejuvenation from the 

 effects of temperature. But if the harmful action is prolonged too far, 

 the primary virulence is lost and the loss is permanent. When this 

 occurs is the bacteriophage dead? Does it still resist destruction for a 

 time? It is impossible for us to tell. 



The dimensions of the bacteriophage corpuscle are approximately 

 those of the serum globulin micella (d'Herelle^^^). Its diameter is about 

 20iJ,{jL (Prausnitz^^"^) . Its chemical reactions show that it is formed of 

 protein substances (de Poorter and Maisin^^)^ 



The vitality of the bacteriophage corpuscle is very great (d'Her- 

 elle^2i)_ Although the number of corpuscles diminish very considerably 

 with preservation for several years, the viability is of much the same 

 order as is that of bacterial spores. 



The colloidal state is determined solely by physical properties, inde- 

 pendent of the chemical constitution or of the living or inert state of a 

 particle. These basic characteristic properties are insolubihty and 

 size. Inasmuch as the bacteriophage corpuscle possesses the properties 

 which inevitably lead to the colloidal state, it naturally exists in this 

 state. From the physical point of view the bacteriophage corpuscle 

 is a colloidal micella. 



