NATURE OF BACTERIOPHAGE 343 



As Beijerinck^* has very justly said, the single fact that the bacterio- 

 phage can undergo an exaltation or an attenuation of virulence is suffici- 

 ent from the point of view of logic to prove that it is a living being.* 



II. It has been demonstrated that the bacteriophage can accustom 

 itself to the harmful action of glycerol.^^^ A mixture of 0.25 cc. of a 

 suspension of Shiga-bacteriophage and of 0.75 cc. of neutral glycerol is 

 made and the tube is sealed. f After a week the tube is opened and 1 cc. 

 of anhydrous neutral glycerol is added. The tube is sealed and shaken. 

 Each week this is repeated; the tube is opened, a cubic centimeter of 

 glycerol is added, and the tube is again sealed. This process is continued 

 up to the point where the total volume reaches 10 cc. 



At this time another mixture is prepared; 0.25 cc. of the same suspen- 

 sion used above and 9.75 cc. of anhydrous neutral glycerol. The two 

 mixtures are incubated at 37°C. When examined after 10 days it is 

 found that the bacteriophage of the second mixture, where the suspen- 

 sion was mixed at one time with the whole quantity of glycerol, is 

 destroyed while in the first mixture, where the glycerol was added pro- 

 gressively, it is still present and virulent. 



Brutsaert^"^ has, in effect, repeated this experiment. He mixed equal 

 quantities of suspension and glycerol, and then evaporated the water. 

 He found that the bacteriophage was destroyed when the evaporation 

 was rapid, but that the virulence persisted when the evaporation was 

 slow. 



III. Prausnitz^^' has shown that the bacteriophage can accustom 

 itself to an antibacteriophagic serum. We know that the serum of an 

 animal prepared by injections of a suspension of the bacteriophage has 

 the property of inhibiting the action of the bacteriophage. Prausnitz 

 progressively increased the quantity of antiserum in a series of bacterio- 

 phage-bacterium mixtures and saw that an adaptation took place. The 

 bacteriophage became resistant and caused bacteriophagy in the pres- 

 ence of quantities of serum which inhibited the action of a non-adapted 

 bacteriophage. 



*Perhaps the strangest feature in all of this discussion is the argument ad- 

 duced by some authors, who, confronted by the evidence which I have furnished, 

 admit that the bacteriophage corpuscle possesses the characters of living beings, 

 but affirm that this proves nothing more than that an inert substance can possess 

 all of the characters of life! It is indeed interesting to see to what reaches of 

 absurdity a preconceived idea can lead one, an idea which gradually becomes a 

 fixed belief. 



t In sealing, a long drawn-out neck should be provided, so that the tube can 

 be repeatedly opened and sealed again in the flame. 



