72 



ROPIXESS IN WATTLE BARK INFUSIONS, 



TiiliU) xiv. — Sources of Carbon {2). 



' Confirmed by a separate test. 



On the first clay of the experiment, Al (6), when plated, showed a pure cul- 

 ture of phase Al. On the eleventh day, B2 (1) contained no living bacteria in a 

 large loop of the medium ; tests Al (2,1 and 7) contained a mixture of the two 

 phases, Al and A2, as well as transition colonies. 



A consideration of the last two experiments leads to the conclusion that in 

 the presence of glycerin the phase Al tends to become A2 irrespective of whether 

 the salt is present a.^ a phosphate or a chloride. With phosphate of soda and 

 the various sugars the teudoncy is for it to remain unaltered. The case is differ- 

 ent with sodium chloride, for levulose, and mannit (and also glycerin) change the 

 phase to A2, the predominance of which gives a permanent ropiness within the 

 limiting time of the experiment. 



The phase A2 tends to change to Al in the presence of dextrose and phos- 

 phate, but not so mucli with the other sugars, while in the presence of citrate it 

 seems to remain unaltered. 



Phase B2 (Table xiv.) is peculiar in giving no ropmess in the presence of 

 glycerin and in the ropiness dissohing in the presence of dextrose. Dextrose ap- 

 pears to have caused the reversion to a phase T?l akin to Al before assisting in 

 the death of the organism. 



Tiie (|uantity of sugar has an influence in determining the ropiness of fluid 

 media. For cxaniple a solution containing 0.25% each of meat extract and 

 sodium pluisphate and 1 . 2 and 5 % of dextrose showed the following 

 with two cultures of Al. Phase Al(l) showed a colony with a granular centre, 

 Pha,se Al(2) had a stipi)lcd centre. These had been picked from a jilate thirteen 

 days previous 1o tlic licninniug of the experiment, and had been transferred daily 

 in bouillon. 



Tt is clear that 2 % and 5 % of dextrose are best for obtaining roi>y solutions 

 with rai-es of Al sliowing colonies with granular centres. The colonies with 

 stippled centres liave lost much of their slime-forming power. The stippling is 



