[SHANLY] HEAT RESISTANCE OF BACTERIAL SPORES 129 



bacillus and allied forms. The various species were grown in pure 

 culture and the suspensions made as already described were subjected 

 for sixty minutes to temperatures ranging in differences of five degrees 

 from 55 °C. to one hundred. Or more accurately, most observations 

 were made first at the temperature of 80 °C. so frequently employed 

 in tests upon spores, and from here onwards successive estimations 

 were made of five degrees difference, both above and below this tem- 

 perature. The accompanying chart affords more eloquently than 

 any words the results obtained. 



In studying the chart and the results therein indicated, it must 

 be called to mind that previous workers have most often afforded the 

 results of fifteen to twenty minute exposures at different temperatures. 

 Many forms which will survive exposure for fifteen minutes at 80 °C. are 

 killed by exposure for half an hour, and yet more by exposure for an 

 hour. The test is distinctly severe. Secondly, whereas in most of 

 the observations there has not been a variation of more than a degree 

 on either side of the temperature indicated, in some there has been a 

 variation of two degrees on either side, thus 80 °C. indicates a tempera- 

 ture which during the hour may have varied between 78 and 82 °C. 

 With rare exceptions the results have been harmonious, occasionally 

 thus there have been forms which have given no cultures after exposure 

 to 85°, whereas a few colonies have survived 90°C. In all such cases 

 careful re- tests have been made so that we believe that this chart affords 

 an accurate table of the termal resistance of the forms employed. 



