BACTERIOPHAGOTJS ULTRAMICROBE 119 



It is difficult to make a direct comparison with the limits of 

 resistance of other micro-organisms, the bacteriophagous ultra- 

 microbe is at present the only one for which such determinations 

 have been made. 3 



The action of glycerine is very interesting. The bacteriophage 

 remains alive for at least two years in a fluid composed of equal 

 parts of glycerine and bouillon or physiological saline. A sus- 

 pension of bacteria in such a medium, a medium in which the 

 bacteria are unable to reproduce, is lysed as perfectly as in or- 

 dinary bouillon, yet in a higher concentration of glycerine the 

 bacteriophage is destroyed. Bablet has in fact shown that 

 when 0.5 cc. of bacteriophage is added to 9.5 cc. of glycerine the 

 ultramicrobe is killed in six days. It may be well to recall that 

 glycerine constitutes the best medium for the conservation of the 

 toxins and diastases. The other known ultramicrobes resist, 

 in general, the action of glycerine. 



We have seen that a suspension in a glycerine medium may be 

 lysed by the bacteriophage, and, as always, the lysed culture 

 becomes a culture of the bacteriophage. If we allow such a cul- 

 ture to evaporate slowly at room temperature we will finally have 

 a residue composed of glycerine, all the water being evaporated. 

 Under such conditions, the bacteriophage becomes adapted to 

 its environment and remains alive in the glycerine residue, al- 

 though it is killed if transferred directly from a bouillon culture 

 to concentrated glycerine. Many instances are known of the 

 adaptation of bacteria to antiseptics; and adaptation is a func- 

 tion of living matter. 



3 1 may cite, for example, the following findings which have been 

 reported, not on the zone of life, but on the zone of growth. 



G. Dernby (Ann. de lTnst. Pasteur, 1921, 35, 277) gives the following 

 figures: 



Staphylococcus pH 4.8 to 8. 1 



B. subtilis pH 4. 5 to 8 . 5 



B. proteus pH 4.4 to 8.4 



B. coli pH 4.4 to 7.8 



The bacteriophage is, therefore, extremely sensitive to the action of 

 bases and acids, since its fatal limit of alkalinity is the same as the limit 

 for growth of ordinary bacteria ; its fatal acid limit is not far distant. It is, 

 therefore, more sensitive than bacteria to concentrations of free H and OH 

 ions. This is further evidence of its living nature. 



