BY R. GREIG SMITH. 403 



arabinose and galactose were obtained. These were identified as 

 in the other cases by the isolation of the osazones and the deter- 

 mination of the melting points. The same substance was not » 

 obtained from the natural gum of Acacia penninervis, but this 

 may be accounted for by the small quantity of the gum which I 

 had at my disposal at that time. 



The growths in test-tubes containing saccharose-potato agar 

 with and without tannin apparently show that tannin has little 

 effect in increasing the quantity of slime. The difference, however, 

 is more marked in plate cultures. In one case the slime scraped 

 off from two similar large plates weighed when dry : — tannin 

 l'624grm., without tannin 1*180 grm. 



In purifying the gum acids it was noted that hydrochloric acid 

 prevents the precipitation with alcohol much more than in the 

 case of the gum acids of Bad. acacice, and sometimes a strong- 

 flocculating agent, i.e., barium chloride, has to be employed. 

 Again, the separation of the bacteria from the gum acids has to 

 be very carefully done if one would obtain the acids in the meta 

 condition. In a second case, when a few drops of dilute sulphuric 

 acid were added and the heating in the autoclave continued for a 

 longer period (45 minutes) the gum acids, after precipitation with 

 alcohol, dissolved readily in water. The insolubility was, how- 

 ever, restored by heating the dried gum acids at 100° for two 

 hours. After this treatment they did not dissolve entirely in 

 water, the fioccules being visible after five days. The gum acids 

 of Bad. acacice, when heated at 100° for the same time, dissolved 

 in water as readily and in the same manner as commercial gum 

 acacia. 



The natural gum of Acacia penninervis, like the bacterial gum, 

 contained the arabinan-galactan complex. 



Summary. — The bacterium which I have named Bacterium 

 metarahinum * was found at the place from which the gum was 

 exuding. It produces a gum which is tough and gelatinous, as 

 evidenced by the consistency of the colonies on nutritive media. 



* Bacillus metarabinus, by Migula's system of nomenclature. 



