536 BIOLOGY OF THE MICRO-ORGANISMS. 



up by a special motor,* or by sounds of sufficient intensity 

 conducted through the nutrient solution,! have a distinct 

 disturbing influence on development. More recently, 

 however, somewhat different results have been obtained 

 in a fresh series of experiments. J 



Influence of Further, a certain medium temperature is a necessary 

 condition for the development of the bacteria. Never- 

 theless, the optimum of temperature, as well as the 

 upper and lower limits, are quite different in different 

 species of bacteria, and are also dependent on the other 

 conditions of life, more especially on the composition of 

 the nutrient material. According to Eidam's experi- 

 ments, with regard to the development of bacterium 

 termo in Cohn's nutrient solution, growth begins at 

 H-5i C., increasing at first slowly as the temperature 

 rises, and then quickly from 10 C. upwards, attains 

 the optimum between 30 and 35 C., and very 

 rapidly diminishes, and ultimately entirely ceases at 

 40 C. In the case of the acetic bacterium the 

 optimum lies between 20 and 30 C. ; below 10 C. 

 growth goes on extremely slowly, and it diminishes 

 rapidly above 35 C., and ultimately ceases a few degrees 

 higher.il The tubercle bacillus grows, on the other 

 hand, only between 30 and 41 C., best at 37 to 

 38 C. In the case of the bacillus subtilis Brefeld 

 found that the growth was very slow at 6 C. ; at 12'5 C. 

 4 to 5 hours elapsed between each new sub-division of 

 the rods; at 25 C., j-hour; at 30 C., J-Lour. From 

 these examples it is sufficiently evident that the various 

 species of bacteria vary markedly with regard to their 

 relation to temperature, and it can only be said with 

 regard to the relation of temperature to the mould and 

 yeast fungi, that as a rule the most favourable tem- 

 perature is less than in the case of the bacteria, in 

 which the optimum lies nearer the temperature of the 

 human body. 



* Horvath, Pfliiger's Arch.f. PhysloL, vol. 17. 



t Eeinke, Ebenda, vol. 23. 



j Tumas, Petersbnrger med. Woch., 1881. 



Eidam, Cohn's Beitrage, i., 3, p. 209. 



|| Mayer, Giihrungschemie, p. 178. 



