TEMPERATURE 41 



MAXIMUM OXYGEN TOLERANCE. 



Atmospheric oxygen, 

 Per cent. 



B. (clostridium) butyricus ........... 1 . 35 



B. chauvei ................ 5.00 



B. edematis maligni ........... . . 3.25 



Purple bacteria (Molisch) ......... about 90.00 



Thiosulphate bacteria (Nathansson) ........ 400.00 



B. prodigiosus .............. 3000.00 



G. TEMPERATURE. 



1. General. The extreme temperature limits of bacterial growth 

 are very slightly above C. to 80 C. inclusive. Some bacteria, 

 notably those found in the Arctic regions, appear to develop even at 

 C.; others, chiefly those found in soil, feces, and certain thermal 

 springs, grow even at 80 C., a degree of heat considerably above that 

 at which the protoplasm of most animals and plants is coagulated. 

 The vast majority of bacteria, however, develop best within a range 

 of temperature from 15 C. as a minimum to 40-43 C. as a maximum. 

 All bacteria exhibit three cardinal thermic points : a minimum tempera- 

 ture, below which growth ceases; an optimum temperature, at which 

 growth is most luxuriant and rapid; and a maximum temperature, 

 above which growth ceases, and the organisms die. Fischer 1 has 

 classified bacteria according to their thermic relations as follows: 



Minimum. Optimum. Maximum. 



1. Psychrophilic bacteria . 15-20 30 Many water bacteria. 



2. Mesophilic bacteria . 15-25 37 43 Pathogenic bacteria and 



others. 



3. Thermophilic bacteria . 25-45 50-55 85 Spore-forming bacteria 



from soil, feces, and 

 thermal springs. 



Bacteria which are progressively pathogenic for man and warm- 

 blooded animals develop within a much narrower range of tempera- 

 ture than the saprophytic bacteria which are found chiefly in nature, 

 as the following table, also taken from Fischer, 2 indicates: 



Difference between 



1 Vorlesungen iiber Bakterien, 1903, II Aufl. 



2 Loc. cit., 106. 



