252 



PHYSIOLOGY OF BACTERIA 



chapter showed a better utilization of food when the 

 concentration was low. If this should mean that a 

 slower fermentation causes a better utilization, we should 

 expect a larger crop at the lower temperatures. How- 

 ever, there is probably a limit to the advantage of slow 

 fermentation. 



Where some specific compound (autotoxin or whatever 

 it may be called) is the limiting factor it may be supposed 

 that it will act similarly to the fermentation products. 

 But because it is a specific compound, the amount pro- 

 duced may have a temperature law of its own. 



Summarizing, the general prediction tends to the 

 assumption that the crop will decrease rapidly as the 

 temperature rises above the optimum, and will increase 



Table 70. — Influence op Temperatuee upon the 

 Micr. pyogenes in Meat Extract 

 (Cells per standard loop) 



Crop" of 



17°C. 



27°C. 



37'*C. 



Start 



After 1 day. 

 After 2 days 

 After 3 days 

 After 4 days 

 After 5 days 

 After 6 days 

 After 7 days 

 After 8 days 

 After 9 days 



632 



2,064 



73,850 



3,120,000 



8,128,000 



12,400,000 



14,512,000 



17,072,000 



18,272,000 



17,592,000 



632 

 5,528,000 

 10,918,000 

 12,568,000 

 14,288,000 

 15,918,000 

 15,664,000 

 13,568,000 



632 

 5,968,000 

 8,744,000 

 10,448,000 

 9,968,000 

 8,688,000 



slowly as the temperature falls below the optimum. 

 There is probably a limit to this increasing crop with 

 decreasing temperature ; we would not expect a maximum 

 crop at the minimum temperature. 



Very few data are available on the influence of tem- 

 perature upon the maximum number of cells. 



