BY R. GREIG SMITH. 



389 



showed that acidity or alkalinity of the medium favoured neither 

 the growth of bacteria nor the production of slime. 



As the function of tannin might consist in slowing the growth 

 of the bacteria, glycerine which appeared to do the same thing, 

 was also employed in an experiment to test the formation of slime. 



Several plates of saccharose-potato agar which contained 

 0-06 grm. tannic acid or 1 c.c. glycerine in every 20 c.c. of medium 

 were prepared. The agar surfaces were smeared with a culture 

 of the bacterium, and the plates were incubated at 22° and 30'' 

 for three days. After noting the appearances of the cultures, 

 the slimes were removed with a rubber spade, and after mixing 

 with water slightly acidified with hydrochloric acid, alcohol was 

 added. The compact or flocculent precipitates were, after wash- 

 ing with alcohol, dried at 100° and weighed. The results are^ 

 summarised in the following table : — 



The results show that it might be possible to obtain a quantity 

 of slime by using tannic acid and by using the lower temperature. 

 They also show how one can be misled by appearances, for there 

 appeared to be much more growth produced on the glycerine 

 medium at 22° than at 30°, while in reality there was a little less. 



On tannin agar the production of slime appears to have finished 

 in from four to five days at 22° C, and the medium assumes a 

 blackish-green colour. If the plate had not been uniforml}^ 

 smeared, and the growth in consequence had formed irregularly, 

 it is noticed that the culture and medium are buflf coloured at 

 the margin, and dirty green in the middle where the growth is 

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