EFFECT OF TEMPERATURE UPON BACTERIA. 147 



45 to 55 C., and for the thermophilic species about 

 75 C. There are no non-spore bearing bacteria which 

 when moist are able to withstand a temperature of 

 100 C. even for a few minutes. A long exposure to 

 temperatures between 80 and 100 has the same result 

 as a shorter one at the higher temperatures. Accord- 

 ing to Sternberg, ten minutes' exposure to moist heat 

 will at 52 C. kill the cholera spirillum, at 54 C. kill 

 the streptococcus, at 56 C. the typhoid bacillus, at 

 60 C. the gonococcus, and at 62 C. the staphylococ- 

 cus, the latter being about the most resistant of the 

 pathogenic organisms which have no spores. 



When micro-organisms in a desiccated condition are 

 exposed to the action of heated dry air the temperature 

 required for their destruction is much above that re- 

 quired when they are in a moist condition or when they 

 are exposed to the action of hot water or steam. A 

 large number of pathogenic and non-pathogenic species 

 are able to resist a temperature of over 100 C. dry 

 heat for an hour. A temperature of 120 to 130 C. 

 maintained for one and a half hours is required to de- 

 stroy all bacteria, in the absence of spores, if dry heat 

 is used. 



Spores are far more resistant to all injurious influ- 

 ences than vegetative forms. They retain their power 

 of germination for years without either nourishment or 

 water, and are much more indifferent to the action of 

 gases than bacilli, the spores of the anaerobic species 

 being especially resistant to the action of oxygen. 

 Spores possess a great power of resistance to both 

 moist and dry heat. Dry heat is comparatively well 

 borne, many spores resisting a temperature of over 

 130 C. The spores of bacillus anthracis and of 



