CLASSIFICATION OF THE COLON-CLOACAE GROUP 



265 



sucrose and dulcitol. Its correlation with other characters is 

 therefore not very marked. 



Indol seems to be correlated with salicin, but the small propor- 

 tion of indol negative strains (10.4 per cent) makes the associa- 

 tion of questionable value, and as the coefficients with other 

 substances are extremely low, indol may be eliminated. 



Glycerol correlates somewhat with salicin (coefficient 0.52) but 



TABLE 3a 

 Coefficients of correlation for each pair of characters in table 3 



with no other character and is therefore not considered desirable 

 for subdivision at this point. 



The choice of a differential character is thus narrowed down 

 to sucrose, raffinose, dulcitol and salicin. Sucrose and raffinose 

 are almost perfectly associated (coefficient of correlation 0.99). 

 Consideration of either therefore suffices for both and as the 

 former is slightly better correlated with other characters, sucrose 

 is selected for further discussion. 



A comparison of salicin with dulcitol indicates that the alcohol 

 is to be preferred. Salicin correlates better with glycerol and 

 indol (the latter relation of questionable value), while dulcitol 

 has higher coefficients with motility, sucrose and raffinose. A 

 similar consideration leads to the choice of sucrose over salicin. 



