GROWTH 



197 



in the original culture. This is shown very clearly by 

 Chesney (1916) who transferred at frequent intervals 

 bacteria from a growing culture of Bad. coli into a fresh 

 medium, and found the rates of multiplication in the 

 new culture for the first two hours after transfer to equal 

 that of the mother culture. Fig. 18 shows in the upper 



Fig. 18. — The parallelism in the growth rates of the parent cultures and the 

 subcultures of Bacterium coli. 



continuous line the logarithms of the numbers of cells 

 in the mother culture. The short lines below are the 

 two hour growth periods of the transferred organisms. 

 The lower lines are practically parallel to the correspond- 

 ing part of the upper line which indicates the same rate of 

 multiplication. A similar agreement was obtained also 

 with cultures of Bad. pneumoniae. 



This explanation implies that the cell mechanism is 

 affected as the medium is gradually changed through the 

 action of bacteria. This change must be more than just 

 an accumulation of fermentation products because it 

 would require only a very short time for these products 

 to diffuse out of the cell into the new medium. As a 

 matter of fact, morphological changes are involved, and 

 the form and size of young, actively growing cells are 

 different from older, slowly multiplying cells as has been 



