COMMUNAL ACTIVITY OF BACTERIA 251 



5. The stationary phase is, as the name indicates, a time of practi- 

 cally no change in the numbers of the bacterial population, and, as 

 is not indicated by the name, a period when the numbers are at a 

 maximum. During this phase the multiplication and the death of 

 cells are practically in equilibrium. 



6. The phase of accelerated death covers the period when decrease 

 in numbers begins slowly, and continues with increasing rapidity and 

 leads into (7), the so-called logarithmic death phase, which covers 

 the mid-senescent period of the cultures at a time when the rate of 

 death sometimes remains constant. Henrici (1928) suggests the 

 addition of (8), a final phase of negative acceleration in death-rate, 



TABLE XXVII 



Showing Penfold's Data Concerning Generation Time 



IN Minutes during the First 2 Hours of 



Growth of Bacterial Cultures 



Dilution of Parent 

 Culture 



since in many cases the death-rate decreases after a time and some 

 cells remain alive after relatively long periods. 



The form of the growth curve of a bacterial culture is influenced 

 by such factors, among others, as temperature, composition of the 

 medium, and the numbers, age, and previous history of the seeded 

 bacteria. Of these, the effect of the size of the inoculum interests us 

 particularly. Evidence clearly indicates that, within limits, the 

 smaller the inoculum the longer the lag phase (Rahn, 1906; Penfold, 

 1914; Montank, vide Henrici, 1928). Penfold's data on the point is 

 given in Table XXVII. Montank used yeast in his experiments. 

 His results are summarized in Table XXVIII. 



Inspection of these tables shows clearly that with the smaller 

 seedings the combined initial stationary and lag phases are pro- 

 longed. With the yeast the prolongation is in proportion to the size 



