FORMS OF THE COLON BACILLUS 137 



variation, and the calcium chloride culture with the highest autoly- 

 sis rate having also the highest index of variation. This is of course 

 only a rank order correlation, i.e., the figures for autolysis rate and 

 degree of variation in cell form vary in the same direction, but not 

 proportionately. But considering the imperfect nature of the measures 

 both of rate of autolysis and variation in form, I believe that this 

 correlation is significant, and offers a real clue as to the nature of the 

 unusual cell forms observed during the death phase. 



It was pointed out in Chapter V that probably the form of bacte- 

 rial cells is maintained by a certain degree of rigidity of the cell walls. 

 If this membrane be softened or destroyed locally, it will lead to a 

 local bulging of the protoplasm, forming lateral or terminal buds or 

 branches or central bulgings depending upon the localization of the 

 area of destroyed or altered cell wall; while if the process involves 

 the entire cell it will give rise to oval and eventually spherical forms. 

 If autolysis be delayed, the dead cells will tend to maintain their 

 form even though the death rate be high. But if autolysis is rapid, 

 and alters the cell wall in the manner suggested, variation in form 

 will be great even though the death rate is relatively low. 



While the differentiation between stained and unstained cells is 

 quite easily made by inspection through the microscope, there is 

 not sufficient contrast in the photographic negative when projected 

 at the magnification used to certainly separate the two classes when 

 making the tracings. Consequently no comparison can be made of 

 the variation in form between the stained and unstained cells. Micro- 

 scopic observation indicates, however, that the majority of the un- 

 usual forms, as budding, branching, and bulging cells, are not stained. 

 This, however, does not necessarily indicate that the variation in 

 form is not due to the same process which leads to the cells becom- 

 ing stainable; the changes in the cell membrane may occur in an 

 earlier stage of the process. 



