:ells of the colon bacillus 



89 



Figure 24 shows in a general way the results of these observa- 

 tions. In this graph the logarithms of the number of cells indicate 

 the rate of growth ; the average length of the cells and the average area- 

 length index having been converted to index numbers, using as the 

 index the mean value of each for the entire period of observation. 

 The data are given in Tables XVII and XVIIL As with Bacillus 

 megatherium, there was noted a very marked increase in the length 

 of the cells during the period of active growth, reaching its maximum 



Fig. 25. 



3 b 9 12 



Hours. 



Representative Cells from a Culture of B. coli at Different 

 Stages of Growth. 



probably again at the point where the growth curve changes from 

 positive to negative acceleration. It will be noted, however, that 

 the curve for area-length index during the early hours of growth 

 is practically the reverse of the curve for length of cells; that is, 

 as the cells increase in length they decrease in area-length index, 

 the longer cells being relatively more slender, even though they were 

 absolutely somewhat thicker. In this graph the average size and 

 form of the cells is indicated by tracings through the major image 

 of composite photographs of the cells prepared as described in 



