54 ROPINESS IN WATTLE BARK INFUSIONS 



tanuiu with certain nutritive substances. These consist partlj- of salts, partly of 

 nitrogenous bodies, probably amido-aeitls akin to asparagin and pai-tly of sugar. 

 The latter is either free or so loosely combined with the glucosidal tannin as to 

 be readily fermentable by yeasts or by B. eoli communis. 



A saline solution containing 2 <"<- dextrose, 0.2 % asparagin and mixed salts 

 was treated with increasing quantities of tannic acid and portions were seeded 

 with the phase B2. The portion with 5 % of tannic acid showed a gi-owth of 

 bacteria but there was no evidence of ropiness. The portions with 2 % and less 

 were ropy in 16 hours. Twenty-five days afterwards, the portion with 1 % was 

 ropy, the others were not and contained fiocculent sediments. This experiment 

 mdi'-ated tliat the organism could develo)i ropiness in fluids containnig dextrose 

 and up to 2 % of tannic acid. This amount seemed to be the limit, as in coui-se 

 of time it slowly coagulated the ropy substance. 



Experiments with Infusions of Bark. 



An infusion of wattle bark was sterilised by filtration through porcelain. It 

 had a Sp.G. of 1.026 at 22° which is roughly equivalent to 5% of tannin. 

 Portions of this infusion were diluted and seeded with bacterium A. subsequently 

 tound to be a mixture of Al and A2. Ropiness appeared in 16 houi-s with the 

 quarter streng-th while the half strength was unaltered . An extension of this ex- 

 periment with more graduated strengths was made with the results as shown in 

 the table. 



Table i. — "Diluted Infusion of Bark. 



Days at 28" 



3 



Bark infusion, diluted. Sp. G., 1.026. 



10 to ion 



1.5 tc 100 



20 to 100 



2.5 to ion 



;io to 100 



35 to 100 



•In this and subsequent tables, "S" indicates a slight ropiness, the 

 Huiil t^ivint; threads varying from oue-sixti'eutli to one-eighth of an 

 inch in length. "4-" indicates tlireads of one quarter of an inch or 

 longer. ■•O" means no apparent ropiness and. in some cases, no 

 groivth. 



The small amount of ropiness obtained with water containing 10 ^'c of the 

 infusion may have been due to ihe paucity of nutrients and the slower appear- 

 ance of the ropiness with 25 <"( and over was possibly caused by the retarding 

 action of the tannin which appeared to hfive coagulated the ropy material liy the 

 6th day. The disappearance of the ropiness may not iiave been entirely due to 

 the coagulation of the ropy substance, for other experin.ents with acids and with 

 salts, wliich will be descrit)cd later, gave indications of a digestion or solution 

 taiing place. 



Some time afterwards, eighty days to be exact, the filtered extract which luid 

 thrown a deposit was dihilid with water in the proportion of three parts of 



