1 84 



C.-E. A, WiNSLOw AND Anne F. Rogers 



We have seen above that the fainter growths are characteristic 

 of the parasitic forms, and the heavier ones of the earth and water 

 cocci. The heavier growths are more common among the packets 

 than with other cell groupings. 



In comparing the vigor of surface growth with the fermentation 

 of carbohydrates, a distinct relation appears at the ends of the scale, 

 although the bulk of the growth, under the headings "good" and 

 "abundant," exhibit uniform characteristics. The "very faint" 

 growths, which denote members of the genus Streptococcus, as pre- 

 viously defined, are associated with a maximum of acid production 

 falling in the highest acidity class in each sugar table. On the other 

 hand, the "very heavy" growths are mainly forms which fail to act 

 on either sugar. 



TABLE 23. 

 Correlation between Surface Growth and Nitrate Reduction. 



Surface growth and nitrate reduction show a suggestive relation. 

 Among the very faint growths of the Streptococcus type no reduc- 

 tion occurs, and almost none among the "meager" forms. The 

 "good" and "abundant" groups show an increasing proportion 

 of reducing organisms, and the "very heavy" group shows many 

 ammonia-formers and a fair proportion of nitrite production. 



TABLE 24- 

 Correlation between Surface Growth and Gelatin Liquefaction. 



With gelatin liquefaction there exists the same group correlation 

 manifest for the other characters. The "very faint" group shows 

 not one liquefier, and the "meager" group very few, while the more 

 vigorous forms exhibit a more even distribution. 



In general, our study of surface growth brings out two distinct 



