COMPARATIVK ( T LIT UAL DAI \. 85 



approximately the same reaction in most cases. Three of these 

 groups show acid and the fourth alkaline tests with litmus. A few of 

 the remaining species continued to grow until after several weeks 

 they reached almost normal development. In such cases the assimi- 

 lation of carbon from lactose seems to be \ery slowly and with diffi- 

 culty accomplished by a large proportioE of the species studied, and 

 to be practically impossible to some species. 



Comparison of t he litmus reactions produced by the various species 

 with cane sugar and with lactose accounts for striking differences in 

 this reaction when litmus is introduced into gelatin or agar media 

 containing these two forms of sugar. A species which will ferment 

 cane sugar and not ferment lactose will produce an acid reaction with 

 one and an alkaline reaction in media containing the other. 



Lactic acid (Tables 4 and 5). — Tubes were prepared containing 

 Dox*s fluid to which 0.9 per cent of lactic acid was added. Thirty 

 forms were inoculated into this medium. Of these forms nine pro- 

 duced normal and typical colonies, showing but slight inhibiting 

 effect from the acid. As manymore cultures slowly became typical 

 colonies. Nearly every form germinated and produced slight growth. 

 In the camemberti group (Nos. 5, 6, 39) and some others the litmus 

 reaction became alkaline. It was thus shown that a series of species 

 could secure carbon from lactic acid and in doing so dest roved the acid 

 character of the medium. The species which grew most rapidly 

 in lactic acid were those which had developed best in the lactose 

 solutions. 



Levulose (Tables 4 and 5). — Tubes were prepared into which 2.5 per 

 cent of levulose was introduced as the source of carbon. The re- 

 sults as tabulated may be seen to group together about the same 

 species as the previous experiments, except that one or two forms 

 were found to grow well in levulose thai failed to grow with lactose or 

 lactic acid as a source of carbon. Fourteen forms produced typical 

 colonies without inhibiting effects, while five more slowly reached 

 typical development. 



Galactose (Tables 4 mid 5). — A series of cultures was made in the 

 same way with '.-> per cent galactose as a source of carbon. Galactose 

 proved much better adapted to supply carbon than either lactose or 

 Levulose. Twenty-five forms produced typical growth, and others 

 grew more or less readily. This form of sugar therefore proved of 

 but small assistance in the separation of species. 



(•hjeerin (Tables 4 an d 5). — Cultures offering carbon in the form of 

 3 per cent glycerin produced much less growth than those containing 

 sugars. Eleven forms eventually reached fairly typical growth; four 

 only of these showed no restraining effect of t he medium. Of these, 

 three are probably closely related if not merely races of a single 

 species — the one most common in general cultural work in this 



