132 THE ROYAL SOCIETY OF CANADA 



of other bacteria which had resisted a temperature of 90°C. for one 

 hour in broth were selected. A uniform loopful of these spores in each 

 case was transferred to a tube containing about one centimetre of 

 broth, and made into a uniform emulsion, and without delay a stand- 

 ard loopful of each emulsion was transferred to the melted agar 

 tubes of the first series, and of the second series respectively. That at 

 40 °C. was immediately poured upon a Petri dish for use as a control. 

 The 90°C. agar was maintained at this heat for one hour, and then also 

 plated. After twenty-four hours the number of colonies on the two 

 plates were compared. The heated showed an enormous reduction 

 in the number of colonies that developed. In fact the vast majority 

 of the spores are destroyed with this length of exposure at this temperature; 

 there are only rare survivors. Thus to give an example, the plates afforded 

 the following results: 



Culture "No. 1." Control 150,000 colonies. Subjected to 90°C. 

 10 colonies. 



B. Anthiacis, Control 37,500 colonies. Subjected to 90°C. 

 2 colonies. 



Here regarding the anthrax bacillus, it must be recorded that we 

 have found the endospores to resist a temperature five degrees higher 

 when heated in agar broth than in plain peptone broth. 



7. Different strains of organisms of the same species are liable 

 to exhibit different resisting powers. This fact has been noted by 

 previous observers. Thus more particularly A. Schmidt^ has called 

 attention to the varying resisting powers exhibited by the spores of 

 B. Chauvei. He, too, has observed that it is only certain of the spores 

 that possess strong resisting powers, the majority being lapidly de- 

 stroyed. He found that the spores obtained from cultures were less 

 resistant than those taken directly from the flesh of animals which had 

 died from Quarter Evil. Several observers, among them Wiel,^ 

 Rokato,^ and Pfeiffer,^ have called attention to the varying resistance 

 of the spores in different strains of the Anthrax bacillus. In our own 

 series it will be observed that we studied two strains of B. Megatherium 

 and of B. Suhtilis respectively, obtained from well accredited sources, 

 and that the two strains show a difference of a few degrees in their 

 maximal thermal resistance. 



Taking all these data into consideration, it becomes evident 

 (a) that in any one culture the spores present exhibit marked difference 

 in the degree of their resistance to moist heat, and (b) that in any one 



^ Inaug. Diss. Bern, Strassburg, 1906. 



«Ctbl. f. Bakt., Abt. 1, 30, 1911, p. 560. 



3 Ibid. Vol. XXXIV, 1903, 725. 



* Zeitschrift f. Mika. u. Paras. Krankh. u. Hy.g.d. Hausthiere 1, 1900, 124. 



