8G ROPIXESS IX WATTLE BARK INFUSIONS, 



transparent ^lun. anil as loose, yellow, sliiucy gi'owtlis. Tlic cohesive ])liase was 

 rapidly cliangetl to the ilittuse phase by growinj;- in s^hieose-selatin at 30°. The 

 gum was a galaetan, hut was liydrolysed witli difficulty, while tlie reactions oT the 

 mucilage were clitt'eretit from those noted with the wattle-hark hacreria. 



( 'iixri.rsioxs. 



The imcstigation was undertaken with the idea of endeavouring to eluciilate 

 one of the i)roblenis that is occasionally' met hy tlie tanner. It is possil)le that 

 every case of ropiness may not he bacterial, hut it may be granted that in the 

 great majority of cases it is a Ijacteriological phenomenon, and any infornuitiim 

 regarding it sliould lie of value. 



To attack the problem from the side of the tannery would he a matter of 

 nnich dilliculty, for one cannot always get cases of ropiness at suital)lc times, 

 and, when rojiiness does occur, circumstances may not be sucli as to facilitate the 

 investigation. That it is not an easy ])roblem is shown by the fact that up to {he 

 present it has not been investigated, and, doubtless, tliis may be traced to the 

 nudti]iiicity of organisms swarming in the tan-li(jUors and tlie habit whicli slime 

 bacteria have of growing in cliiin])s. while most of the other bacteria diffuse 

 themselves. It apiieared to be an easier way to attack tlie problem from another 

 aspect, that of the ropiness that occurs in wattle bark infusions, and there is 

 every reason to believe that the results obtained with the infusiims will he laiucly 

 applicable to tanning li(|uors. 



In the bark of wattle trees, many bacteria may he capable of producing ropy 

 infusions, but so far only two have been found. They are closely allied to one 

 another and differ, not so much in their bacterioscoi>ic characters as in their phy- 

 siological properties, that is, in their ])ower of forming the ropy substance under 

 different conditions, especially as regards nutrition. The bacteria lia\'e been pro- 

 visionally named A and B. Like several gum-formiug bacteria which have been 

 descrilied by the writer,* each bacterium can show two phases, one forming' a 

 comparatively soluble slime, the other giving a viscous slime. 



The pos.session of two phases is not unique and possibly a double phase may 

 be expected to occur with many slime-forming bacteria. The alteration of phase 

 is possibly associated with the presence or comparative absence of a gum-digesting 

 enzyme. The soluble phase certainly possesses a larger amount id' a gelatine- 

 dissolving en/.yme, and one can, at will, by altering the incubation temi)erature, 

 obtain a mobile or a viscous fluid. 



There appears to be something in liark infusions that induces the snliilile 

 phase to become the insoluble phase and gives rise to ropiness. 



The tannins of hark infusions liave a prohibiting action upon the formation 

 of ropiness, cm account of their property of co.ag'ulating the slime, and for this 

 to occur a certain concentration is necessary. For Racterium .\ this is e(|uiva- 

 lent to a specific gravity of 1.024, and for Bacterium B, 1.048. Pure tannic 

 acid is more active, for the prohibiting amount is much under the (|iianlities of 

 tannin represented by the gravities of the infusions. In synthetic media. 2 '^ r of 

 tannic acid prevents the formation of ropiness by coagulating the slime, as it is 

 formed, upon the bodies of the bacteria. 



In view of this differenti.nl action of tannin as compared with tannic .-ii-id. 



'Tlie liaotei-iii rusponsible for tlic |iv<iiluctiou tif the soIuMe :iud uisolulile wattle 

 gums were uained /I. ticaciae aud /?. iiiitunihiiniiii, and it was shown tliat the one form 

 could lie nlterc'il ti) the other. //. .U/irrsloiiei fthese Proceedings, liKH. H'i) exists as 

 two phases, .me tunning a sqlulilc sliuie. the .■tlu-r ]iroducing !in insoluble gelatinous 

 gabictau. 



