BY R. GREIG SMITH. 387 



copper, lead, silver and mercury and to the hydrates of calcium 

 and barium in a manner precisely similar to a solution of com- 

 mercial gum arabic and to the bacterial slime. 



The next step was the testing of the slime for pentosans. A 

 portion was distilled with hydrochloric acid of sp.g. 1'06, and the 

 distillate on treatment with a hydrochloric acid solution of 

 phloroglucin yielded the furfural reaction. Another portion was 

 carefully heated with strong sulphuric acid, and the volatile 

 products gave the furfural rose colour to paper moistened with 

 aniline acetate. These reactions were also obtained with portions 

 of the natural gum of Acacia penninervis. The bacterial slime, 

 therefore, contained pentosans as evidenced by the production of 

 furfural on treatment with acids. 



As I have already said, the cultures upon an artificial medium 

 made up from a few constituents were not very successful. This 

 medium contained saccharose, peptone, glycerine, potassium phos- 

 phate and chloride, and agar in proportions that experiment 

 seemed to indicate as being suitable. Agar must be employed, 

 because, although on all gelatine media masses of slime enclosing- 

 bacteria can be observed, yet, as the medium is slowly liquefied 

 by the bacterial products, the slime would be contaminated with 

 peptonised gelatine. In the course of experimenting with various 

 media, potato-extract agar gave a good growth, and this was 

 increased by the addition of glucose or saccharose. But even 

 this growth was not what would be called rich in gum or slime. 



At this stage several observations were made. After scraping 

 the culture from the surface of saccharose-potato agar, the plates, 

 which had been incubated at 30°, were allowed to stand at the 

 laboratory temperature (15°) for several days, when a quantity of 

 slime greater than the original crop at 30° was obtained. This 

 appeared to indicate that a lower temperature and a slower growth 

 was accompanied by relatively greater slime formation. In 

 separating the bacteria from the tissues of a specimen of gum- 



