[malone-shanly] resistance OF B. ANTHRACIS SPORES 87 



Table I. 



Strain heated one hour at 



80°C. 85°C. 90°C. 



316 + +1 - 



O.S.C.(l) + +1 - 



O.S.C.(2) + +2 - 



H.L + + - 



Borden Mule + + - 



108 + 



Burt + - - 



Boerner + — — 



Falfurias + — — 



Davis + — — 



6071 + - - 



107 + 



109 + 



6087 + 



Studying the above table together with the character of the 

 different strains above recorded, it will be observed that no correlation 

 is to be made out between any one feature, such as viscosity, strength 

 of Gram positive staining, square endedness, etc., and heat resistance 

 of the spores. The one obvious feature is that strains of the B. 

 Anthracis vary in their heat resisting power. It is not possible to lay 

 down that there is a specific thermal death point for Anthrax spores. 



Following upon these observations the question presents itself 

 as to whether or not this same variation exists between spores of the 

 same strain of a species. With a view to ascertaining this point the 

 following experiment was made and the results recorded in Table II. 



Two cultures were selected, Davis and 607^ 



1. These two cultures were subjected to temperatures of 80°, 

 85°, and 90°C, for periods of five, fifteen, thirty, and sixty minutes. 



2. Spores from these were transferred on the point of a platinum 

 needle into a cubic centimetre of broth which was then well shaken 

 up. A loopful of these emulsions was transferred to the heated broth 

 tubes in the water-bath. After the required exposure a loopful of 

 this broth was transferred to agar, which was plated. The plate 

 cultures were left to grow for forty-eight hours, when the number of 

 colonies, each representing a surviving parent spore, was counted. 



^ Scanty growth in 24 hours. 

 ^ Scanty growth in 48 hours. 



