590 THE GUM FERMENTATION OF SUGAR CANE JUICE, 



10 % saccharose, that is to say, the solutions did not become 

 ropy and capable of being drawn into threads as in the 

 case of fluid cultures of many slime-forming organisms. The 

 bacteria were further cultivated in nutrient agar with 20 % 

 saccharose. One of the organisms formed raised transparent 

 mucilaginous colonies, which made it appear probable that it was 

 the most likely organism to produce "gum." This became more 

 probable when short viscous threads were formed on raising the 

 cover from a Petri dish, in which a pure culture had covered the 

 surface of the agar and grown up the rather low side of the dish. 

 A gummy substance had apparently been formed by the bacterium, 

 but since no apparent viscosity had been produced in saccharose 

 fluid media, it was desirable to test the fluid cultures more 

 rigorously for viscosity. 



Viscosity Produced in Solutions of Saccharose. 



With this object in view, an infusion was prepared from 1,000 

 grms. of grass and 1,000 c.c. of tap water, and to this 200 grms. of 

 cane sugar were added. A 500 c.c. sterile portion was inoculated 

 with the organism and incubated at 28° C, with a check 500 

 c.c, test. On the third day a viscous film was observed floating 

 upon the surface of the infected medium, and partly adhering to 

 the glass of the culture flask. On the fifth day the culture, with 

 its floating zooglcea films, was boiled, and during the process it 

 was observed to foam very much, as if the solution contained 

 carbon dioxide, while the control test, on being similarl}^ treated, 

 boiled quietly. Both fluids were then filtered through paper; 

 the culture filtered slowly, and the zoogioea films were retained 

 on the filter. The fluids were brought to a uniform temperature 

 (24° C, the air temperature being 22° C), and allowed to run 

 from a 100 c.c. pipette, provided with a narrow outlet, and 

 having two marks on the stem, one above and the other below 

 the bulb. The time taken by the surface of the fluids in passing 

 from the upper to the lower mark was noted. For purposes of 

 comparison, the viscosity of other solutions was determined in 

 the same apparatus and at the same temperature. 



