(iO ROPINESS IX WATTLK HARK IXFUSIONS 



temperature uo ropiness developeil. Then the fiask was trausf erred to au iu- 

 cubator at 28° and the culture became strongly ropy, the brownish ropy blobs, 

 one (it which was about two inches iu diameter, were clearly shown against the 

 milky chalk suspension. The flask was returned to the incubator at 37° when 

 the ropiness disappeared. Once more the ropiness appeared at "28°. These ob- 

 servations clearly show that a digestion of the ropy substance occurs at 37° in a 

 neutral solution. An acid reaction of the medium is not essential for the diges- 

 tion of the slime but it is possible that it may assist. 



That the temperature has mucli to do with the speed of the digestion of tlie 

 slime was shown in a test in whicii jihase Al was grown at 22° and at 28°. 

 Both were ropy on the second day. the 28° test was limpid on the 5th and the 22° 

 test on the 8th day. 



The experiment with chalk suggested the secretion of a slime-dissolving enzyme 

 by the i>hase Al. Prolmbly this is so but when experiments were made in which 

 old fluid cultures of Al were added to lumps of the purified gelatinous slime of 

 A2 in presence of an antiseptic, no solution of the slime was ol)tained. 



It became evident that phase Al was capable of forming and eventually 

 digesting the ropy substance. It also rapidly dies out and it may be noted in 

 this connection that it jn-oduces a more rapid liquefaction of gelatine. If the 

 A2 phase is used originally, the ropy substance may j)ersist, while if a mixture 

 of the phases is initially present, digestion occurs, but at a later period than in 

 the case of the pure Al phase. It seemed to be entirely a question of the rela- 

 tive numbers of the two phases during the period of bacterial growth. Instances 

 of the autodigestion of the ropy material will be found in tlic exiiciiments with 

 the various svfgars and salts. 



Change uf Phase. 



These observations led to testing the reversion or alteration of the pha,ses. 

 It had been noted that glycerine favoured the production of ropiness from phase 

 Al and that dextrose did not or, if it did, the ropy fluid subsequently became 

 limpid. This was confirmed in experiments subsequently recorded with sugars, 

 etc., where i-opiness slowly developed and persisted in the presence of glycerine 

 but did not persist when other sources of carbon were used. 



-V specific test was made with cultures of the phases Al and A2 taken from 

 ]iuic colonies and grown in broth for one day before being seeded into tlie test 

 bottles. Phase Al was .sown in a fluid containing glycerine, meat-extract and 

 sodimu phosphate while phase A2 was grown in dextrose with mixed salts as on 

 p. .58. Rotli tests were ropy on the third day, and on tile thirteentli day, phase 

 Al in the glycerine was quite ropy, while phase A2 in the dextrose was limpid. 

 Plates were piepared on the thirteentli day and these showed that piiase Al con- 

 sisted of a mixture of typical colonies of phases Al and A2, and that iiha.se A2 

 hail licen altered into more or less vacuolated colonics of phase Al . 



The experiment conclusively slmwed that the phases were reversil)h'. 



The Action uf I'lnniic Acid. 



The bacterium B2 was peculiar in giving iiroiKJunced riqiy solutions when 

 seeded into infusions of wattle l)ark of increasing strength and little ropiness in 

 synthetic liiiiiids. The reason for this could only he explained liy testing tlie 

 various nutrients in tlie presence of the nearest approach to the tannins avail- 

 able. niiiMch laiiriic acid. It imiv lie that the tannins in wattle bark infusions 



