98 ATLAS OF BACTERIOLOGY. 



demonstrable injurious influence upon bacteria which 

 remain absolutely undeveloped in pure carbonic acid 

 (C. Fraenkel: Z. H., Y.) 



Sulphuretted hydrogen in large amounts is al- 

 ways an active bacterial poison; small amounts kill 

 the bacterium Pfliigeri very rapidly (Lehmann and 

 Tollhausen: C. B., V., 785). 



6. INFLUENCE OF TEMPERATURE ON THE LIFE OF 

 BACTERIA. 



Each variety of bacteria makes certain demands 

 upon the temperature of its nutritive medium. Vege- 

 tative bacterial life is possible from to about 70, 

 but there are some varieties which flourish at the 

 lower range, others at the upper range. In each 

 variety the minimum and maximum of temperature 

 are separated by about 30, and the following com- 

 prehensive classification may be made according to 

 the temperature requirements : 



PsychropJiilic bacteria : minimum at 0, best at 15- 

 20, maximum at about 30. These varieties usually 

 live in the water. They include, for example, many 

 phosphorescent bacteria of the ocean (vide Forster : 

 C. B., XIL, 431). 



Mesophilic bacteria: minimum at 10-15, best at 

 37, maximum at about 45. These include all the 

 pathogenic varieties, because acclimatization to the 

 bodily temperature is a necessary condition of their 

 pathogenic action. 



Bacillus vulgatus, * which still thrives at 50, fur- 

 nishes a transition to the following group. 



* Bacillus vulgatus thrives at from 15-50, and one variety of 

 Globig's ranges from 51-68, but such cases are very rare. Glo- 



