286 THE BACTERIOPHAGE AND ITS BEHAVIOR 



At all events, it is certain that, as a general rule, the weakest virulence 

 disappears first, but we should not overlook the fact that there are many- 

 exceptions to this rule and it is well to consider that each race of the 

 bacteriophage may behave in its own individual way. 



If a bacteriophage suspension is allowed to evaporate slowly at room 

 temperature it is found that living corpuscles may be found in the few 

 drops of syrupy fluid remaining in the bottom of the tube. Indeed, 

 certain bacteria act in the same way. On the contrary, living corpuscles 

 are no longer to be found after twelve months in glucose bouillon cul- 

 tures, although they may still be alive in lactose bouillon. 



From fecal material preserved at room temperature in sealed tubes 

 for thirty-four months (September, 1915, to July, 1918) it was possible 

 to recover the living bacteriophage, as active as at the beginning. 

 This experiment has been performed successfully with four specimens 

 of feces from convalescent cases of dysentery. 



In a mixture of equal parts of neutral glycerol and of bacteriophage 

 suspension, held for five years in sealed tubes, the virulence of the 

 bacteriophage corpuscles (Shiga-bacteriophage) remained unimpaired. 



It is noteworthy that the liquid in which the corpuscles are sus- 

 pended exerts a considerable effect upon their preservation. As for the 

 reaction of the liquid, the effects of acid are once more evident, for if the 

 fluid is ever so little acid the period of the conservation will not extend 

 beyond a few weeks, when the tubes containing the corpuscles are held 

 at laboratory temperature. 



On the question of the preservation of the bacteriophage in the dry 

 state I have several apparently contradictory facts. 



In 1916 I placed some drops of filtrate (Shiga-bacteriophage) upon 

 some sheets of filter paper. These were dried and then aseptically 

 transferred to glass tubes which were sealed in the flame. These tubes 

 were left in the laboratory, exposed to the light, for 6 months. At the 

 end of this period a fragment of the filter paper, introduced into a tube 

 containing a suspension of Shiga bacUH, caused bacteriophagy.^^^ 



Seiffert^^^ has taken exception to this, and quite correctly, for it has 

 been impossible for me to repeat this experiment, although I do not yet 

 see any possible cause for error which has not been considered. Did 

 the nature of the filter paper play any role? In this same connection 

 it may be added that Gerretsen, Gryns, Sack and Sohngen^-^ have found 

 that their bacteriophage, virulent for B. radicicola, remained active 

 for two months when dried on filter paper. 



If a suspension of the bacteriophage is allowed to dry slowly at room 



