118 THE BACTERIOPHAGE 



It may be concluded from these experiments that all strains 

 of the bacteriophage react to temperature in the same manner. 

 When heated above 60°C. they are attenuated more or less rapidly 

 according to the bacterial species upon which they operate. All 

 are completely killed, or at least paralyzed, at about 75°C. 



Chemical agents 



The bacteriophagous ultramicrobe will attack bacteria either 

 in the presence or absence of oxygen, or indeed in an atmosphere 

 of either nitrogen or hydrogen. 



Antiseptics 



It is interesting to study the action of antiseptics for these 

 substances do not act in the same manner on certain ultramicrobes 

 as on ordinary bacteria. While very sensitive to the action of 

 certain antiseptics, they are very resistant to others. 



A culture of anti-dysentery bacteriophage in physiological 

 saline 2 is distributed into four tubes. One serves as a control. 

 The second receives mercuric chlorid to a concentration of 1:200, 

 the third receives copper sulfate to a concentration of 1:100, 

 and to the fourth phenol is added in a concentration of 1 : 100. 

 After contact with these substances for three days the bacterio- 

 phage is living in all the tubes. After four days it is killed in the 

 tubes containing the mercuric chlorid and the copper sulfate. 

 After seven days it is killed by the carbolic acid. It remains 

 alive in the control tube. 



It is not killed after contact for a week in a fluid saturated 

 with essence of thyme or of cloves, but its lytic action is not mani- 

 fested there. The same results are secured in media containing 

 chloroform or sodium fluoride (Bablet). 



Eliava and Pozerski have determined with precision the lethal 

 limits, in 24 hours, of concentrations of free H and OH ions. The 

 zone compatible with life lies between pH 2.5 and 8.54, corre- 

 sponding approximately to an acid 1/160 JV, and a base 1/260 

 N, whatever may be the acid or alkali tested. 



2 Bouillon is not suitable for this work because of the precipitates which 

 form upon the addition of certain antiseptics. These give rise to entirely 

 false results. 



