GROWTH 201 



cause of a cessation of growth. These products, then, 

 must also bring about the morphological changes and 

 change the actively growing and fermenting cell into a 

 resting cell, and thus cause the lag if these cells are 

 transferred. 



It cannot be, though, that small amounts of this 

 peculiar cell secretion are transferred with the inoculum, 

 and bring about retardation. Then, we should expect 

 the lag period to be more pronounced with a larger inocu- 

 lum, while the opposite is the case as shall be shown 

 presently. 



It can be only that the cells have gone into a resting 

 stage, morphologically and physiologically different 

 from that of the active cells, and that some time is 

 required to change from one stage into the other. The 

 assumed cell secretions will bring about this change, 

 but have no further effect after the change of the cells 

 has been accomplished. 



This explanation does not satisfy entirely, for it does 

 not account for the fact that the lag period is shorter 

 when the inoculum is larger. This has been shown by 

 many investigators, (Rahn, 1904, Penfold, 1914, Graham- 

 Smith, 1920) and is illustrated graphically (Fig. 19) 

 from some data by Henrici, (1928), showing the multipli- 

 cation of yeast in a medium of 2% peptone + 10% 

 glucose. 



Cultures 4, 5, 6, and 7 had 10, 100, 1,000, and 10,000 times as 

 many cells at the start as culture 3. They are all drawn here with 

 the same starting point, and therefore, the number 5 on the ordinate 

 scale means 5,000 cells in case of culture 3, and 50,000,000 in case of 

 culture 7. If the cultures all grew at the same rate, their curves 

 should fall on the same Hne. They differ greatly, however, and 

 culture 7, with the largest inoculum, overcomes the lag most rapidly, 

 while the others follow in order of their cell concentration. 



