400 BACTERIAL ORIGIN OF GUMS OF ARABIN GROUP, 



in this method of growth a strong indication that the slime is 

 more insoluble than that secreted by Bact. acacice. On saccharose- 

 potato agar with or without tannin Bact. acacice produces at 15° 

 a gummy slime that does not adhere firmly to the medium. The 

 other bacterium forms a thicker slime, and the portion in contact 

 with the medium adheres firmly and cannot be entirely removed 

 with a rubber spade. When the two slimes are carefully removed, 

 dried in the steam bath at 100° and then moistened with water, 

 the slime of Bact. acacice swells up, forming a diffusive slime very 

 similar to its original condition, while the slime of the other bac- 

 terium smells slightly and retains the shape in which it had 

 dried. There is thus a strong probability that the new bacterium 

 forms the insoluble gum (the meta-arabin) of wattle gum. That 

 the slime might eventually prove to be of the arabinan-galactan 

 class was indicated by the great similarity of the growth on 

 tannin-saccharose-potato agar with that produced by Bact. acacice. 



The nature of the slime had now to be determined, and as with 

 Bact. acacice, large plates of tannin-saccharose-potato agar were 

 infected with a suspension of the bacteria in 10 c.c. of normal 

 saline, and these were kept at the laboratory temperature (15°). 

 The slimes wers collected, rendered more acid with a few drops 

 of dilute hydrochloric acid and treated with alcohol. A curdy 

 precipitate which became cohesive and an opalescent solution 

 were obtained. The precipitate was stirred repeatedl}' with 

 alcohol until no further opalescence was produced. The pre- 

 cipitate was treated with water and then with alcohol, when a 

 thin starch paste-like suspension was produced. This was 

 flocculated with barium chloride (potassium chloride did not act 

 so well as the barium salt), and a contractile curd separated from 

 an opalescent solution. The opalescent alcoholic solution was. 

 added to the opalescent solution previously obtained and the gum 

 in this was precipitated by the addition of barium hydrate and 

 reserved for future examination. 



The contractile curd was treated with water, with which it 

 formed a thick paste. The lumps were broken up by passage 

 through a wire-gauze filter and the whole was warmed to cause 





