298 THE BACTERIOPHAGE AND ITS BEHAVIOR 



The suspension used was a Coli-bacteriophage, active in a dilution 

 of 10-7. 



After exposure for 30 minutes at 46°C. it was still active at 10~^ 

 After exposure for 30 minutes at 48 to 54°C. it was still active at 10 ~^ 

 After exposure for 30 minutes at 56 to 62°C. it was still active at 10~^ 

 After exposure for 30 minutes at 64°C. it was still active at 10~* 

 After exposure for 30 minutes at 66°C. it was still active at 10~^ 

 After exposure for 30 minutes at 68°C. it was inert 



Bacteriophage corpuscles, without regard to what race they belong, 

 are always more resistant than are the homologous susceptible bacteria. 

 We have seen elsewhere that Bordet and Ciuca have taken advantage 

 of this property to isolate the bacteriophage. By heating a secondary 

 culture, or a mixed culture, at about 58°C. the bacteria wUl be killed 

 whUe the bacteriophage will not be entirely destroyed. But although 

 they are not destroyed we now know that an attenuation in the virulence 

 of the corpuscles begins at a temperature well below 58°C., and from this 

 it is evident that this method of isolating the bacteriophage should 

 never be used when it is desired to carry out experimental work free of 

 all criticism. FUtration through a candle or ultrafiltration through a 

 membrane with large pores is always to be preferred. 



Employment of this defective method of isolation opens the way for a 

 number of errors, all too frequently appearing in some of the published 

 work, which might readily have been avoided with a satisfactory 

 technic. Gildemeister, a very skillful bacteriologist, has recently ob- 

 tained questionable results because of such an error. 



Some time ago I stated^^^ that experiment seems to show that cor- 

 puscles are more sensitive to heat immediately after bacteriophagy 

 than they are several days later. Tomaselli^^^ has now confirmed this 

 fact, and his experiments are here presented in summary. 



A Shiga-bacteriophage was used, the tests being made immedi- 

 ately after dissolution was completed and again two days later. (See 

 table 28.) 



That the bacteriophage corpuscle appears to undergo a diminution 

 of volume during the first few days after the bacteriophagic process is 

 completed has been stated above. We now see that during this same 

 period it appears to acquire a somewhat greater resistance to heat. 

 This must be the result of a condensation of the corpuscular substance. 



The only author who has measured the resistance of the bacteriophage 

 when in the dry state is Hauduroy, who found that it was destroyed 

 at a temperature of 135°C. 



