892 



TRANSACTIONS OF SECTION K. 



monotonous regularity, and so the number or mass of bacteria present would 

 double itself every n minutes. This may be accepted as the ideal condition. 



The following actual experiment may be quoted to show that for a time the 

 ideal rate of growth is maintained, and that at the end of every n minutes there 

 is a doubled amount of protoplasm capable of catalysing a doubled amount of 

 chemical change and carrying on a doubled growth and development. 



From a culture of Bacillus typhosus in broth at 37° C. five small samples were 

 ■withdrawn at intervals of an hour, and the number of bacteria per unit volume 

 determined by the usual procedure. The number of organisms per drop 

 increased in the following series: 67, 14-4, 331, 70-1, 161-0.' This shows a 

 doubling of the mass of bacteria in every fifty-four minutes and is the case actually 

 represented in the strictly logarithmic curve of fig. 2. 



i6o 



l« 



'\00 



5o 



lio 



HouA-4 11 I 



Fig. 



3 A- 



We may quote some observations made by E. Buchner- of the rate at which 

 bacteria increase in culture media. Bat illus coli communis was grown at 37° C. 

 for two to five hours, and by comparison of the initial and final numbers of 

 bacteria the time required for doubling the mass was calculated. Out of twenty- 

 seven similar experiments a few were erratic, but in twenty cases the time for 

 doubling was between 19-4 and 24-8 minutes, giving a mean of 22 minutes. This 

 produces an increase from 170 to 288,000 in four hours. No possible culture 

 medium will provide for prolonged multiplication of bacteria at these rates. 



Cohn ' states that if division takes place every sixteen minutes then in twenty- 

 four hours a single bacterium 1/i long will be represented by a multitude so 



' For this unpublished experiment on bacterial growth I am indebted to Miss 

 Lane-Claypon of the Lister Institute of Preventive Medicine. 



- Buchner, Zan-achsgrossen u. Wachsthuvisgeselovindiglteiteii, Leipzig, 1901. 

 = Cohn, Vie Pjtanze, Breslau, 1882, p. 438. 



