No. 502] CHEMICAL MECHANICS IN LIVING PLANT 



<)49 



five hours, and by comparison of the initial and final num- 

 bers 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 cul- 

 ture medium will provide for 

 prolonged multiplication of 

 bacteria at these rates. 



Cohn s states that if division 

 takes place every sixteen min- 

 utes then in twenty-four hours 

 a single bacterium 1 long will 

 be represented by a multitude 

 so large that it requires 

 twenty-eight figures to express 

 it, and placed end to end they 

 would stretch so far that a 

 ray of light to travel from one 

 end to the other would take 

 100,000 years. The potentiali- 

 ties of protoplasmic catalysis ou;u * 1 

 are thus made clear, but the 



actualities are speedily cut short by limiting factors. 



For a while, however, this ideal rate of growth is main- 

 tained. At the end of every n minutes there is a doubled 

 amount of protoplasm present, and this will be capable 

 of catalyzing twice the amount of chemical change and 

 carrying on a doubled amount of growth and develop- 

 ment. This is what common sense and the law of mass 

 alike indicate, and is exactly what this logarithmic curve 

 in Fig. 2 expresses. 



This increase of the amount of catalytic protoplasm 

 by its own catalytic activity is an interesting phenomen- 

 on. In Section K we call it growth, attribute it to a spe- 



