C.-E. A. WINSLOW 



65 



favorable conditions of medium and temperature the cells of bacteria may divide once 

 in 17-20 minutes, while under less favorable conditions the rate of multiplication 

 may be slackened to any desired degree. 



TABLE II 



Typical Generation Times during the Phase of Logarithmic Increase 



Observer 



Conn, 1918 



Jordan, 1926 



Frankland, 1894 



Whipple, 1901 



Harrison and Vanderleck, 1909. . 

 Buchner, Langard and Riedlin 



1887 , 



Barker, 1908 



Type of Organism 



Soil bacteria 

 Bad. coli 

 Water bacteria 

 Water bacteria 

 Bact. coli 



V. cholerae 

 Bact. coll 



Medium 



Temperature, "C 



Generation Time, 

 Minutes 



840 

 720 

 196 

 IIS 



40 



19-40 

 17 



The most obvious of the environmental conditions which determine the genera- 

 tion time — and hence the K in the curve for rate of logarithmic increase — is the tem- 

 perature (see Ward, 1895). The results of certain of the most exhaustive studies on 

 this point are cited in Table III. 



^ TABLE III 



Generation Time at Various Temperatures in Minutes 



Observer . 



Organism . 

 Medium. . 



Whipple 



Water bacteria 

 Bottled sample 



Harrison and 



Vanderleck 

 Bad. coli 

 Milk 



Buchanan 



Bad. coli 

 Broth 



Lane-Claypon 



Bact. coli 

 Broth 



Temperature, ° C. 



864 



15- 

 17- 

 20. 



25- 



30- 

 31- 

 34- 

 35- 

 37- 

 40. 

 42. 



720 

 '386' 



4S0 



143 

 '56 



45 



180 



76 



43 

 29 



17 



52 



32 

 28 



19 



If we plot the logarithms of these generation times against temperature, we obtain 

 a series of straight lines, as was pointed out by Lane-Claypon (1909). The increase in 

 rate of growth is approximately doubled for a 10° C. rise in temperature, a relationship 

 which Snyder (1908, 1911) has shown is as generally characteristic of biological proc- 

 esses as of chemical reactions. 



We may next consider briefly some of the other factors which determine the rate 

 of logarithmic increase — a problem by no means easily elucidated. It is easy enough 

 to understand why bacteria increase when inoculated into a rich, sterile culture me- 



