88 MORPHOLOGIC VARIATION 



cell as long as this is symmetrical about both axes. It will be at 

 once apparent, however, that this does not serve if the cell is at 

 all asymmetrical. If, for instance, we have bulgings or constrictions 

 or lateral projections, such unusual cell forms might have the same 

 area-length index as a cell which was quite uniform throughout. 

 With the early stages of growth, however, such asymmetrical cells 

 are exceedingly rare, and therefore for this stage the area-length 

 index serves very well to indicate the variations in form of the 

 cells. By the use of this measure, together with the length of the 



7 



2X 



193 



100 



50 



l|lllM 



Logajrithms of Numbers of Cells 



— Index Kuiabers of Area-Length Indices. 



Index Numbers of Average Lengths of pells. 



Index Numbers or Average Lengths ot pe 



3 w 9 12 18 30 ^ 72 9d 



Hours. 

 Fig. 24. Growth Curve and Morphologic Variations of a Culture of 



B. coli. 

 From "A Statistical Study of the Form and Growth of Bacterium coli." Re- 

 produced through the courtesy of the Society for Experimental Biology and 

 Medicine (Proceedings, 1923, 21, 215). 



cells, we can therefore follow consecutive changes both in the size 

 and the form of the cells, and correlate these with each other, as 

 well as with the rate of growth. 



The organism used was an old laboratory strain, a typical colon 

 bacillus. The culture was inoculated onto agar slants, following the 

 technique described in Chapter III. Samples were removed for 

 counting and measurement every three hours for the first twelve 

 hours, and again at eighteen, thirty, forty-eight, seventy-two, and 

 ninety-six hours. 



