58 



ROPINESS IN WATTLE BARK IXFVSIONS 



of ropiness. When tbe acidity is greater the ropy material assumes the tloeculent 

 condition. In most cases the ropiness was evanescent and soon disappeared, a 

 circumstance which was subsequently traced to the presence of the phase Al. 

 The acidity in the presence of dextrose probably increased, for the portions with 

 -f-15° of original acidity showed -(-20° at the end of the experiment. 



Another test was made with glycerine, using 0.5 % of the hydrated phosphate 

 of soda instead of the usual mixture of salts. The medium as prepared was 

 neutral to methyl-red and portions were acidified with jiliosjihoric acid. 



Table iv. — Glycerine with increasing acidity. 



On the eighth day the portions infected with phase Al showed, in the case 

 of the 12.5° and of the 15°, the presence of transition forms. The original 

 acidity decreased as time went on; on the seventeenth day, the test with an 

 original acidity of -|-5° had become +3°. -|-1()° had become -|-5°. and -|-2n° had 

 become -\-7° to methyl-red. 



The original acidity of a glycerine medium does not seem to liave much in- 

 fluence upon the production of ropiness, but this may be explained by the fact 

 that the acidity is reduced during the growth of the organism. 



The acidity of spent tan liquors seems to vary from -|-12.5° to -(-20° by 

 Proctei''s lime water test, and one which was tested showed -|-10.4° by this test 

 and -(-5° by methyl-red. So far as mere acidity is concerned, the organism 

 should produce ropiness in such an end-liquor, but when tested it did not do so. 



The Disappearance of Ropiness. 



The disappearance of the ropiness in cultun' fluids was noted first in the 

 case of B2 when growing in a medium containing saccliarose 2^r. meat extract 

 0.5 % and mixed 'salts (KH.l'O^, 0.2 %: MgSO+ Aq. 0.1 %; CaCIo, 0.02 %) 

 made neutral to methyl-red. The fluid was ropy on the fourth day at 28° and 

 quite limpid on the 6th when the acidity had risen to -)-8° . Again the experiment 

 with varying amounts of acid noted on p. 57 showed a solution or digestion of the 

 ropy material in the case of A. a mixture of Al and A2. 



The speed in the digestion of the ropy substance was tested up(in several oc- 

 casions by growing tlie phases of the bacteria in medium containing 2 ''c of 

 dextrose witli meat extract and mixed salts at 28°. The bacterial phases had 

 been picked fi-om agar plates and were typical, that ij to say, they were the 



