BY R. GREIG SMITH. 241 



An experiment was made in which levulose was added in vary- 

 ing amounts to the potato medium, and the following results 

 were obtained : — 



The x\ddition of Levulose to Potato-extract. 



Slime in grams from 100 c.c. of medium/ 



No levulose 

 Levulose 1% 



„ 2% 



„ 3% 



,, O O /o 



None 

 8 

 15 

 21 

 23 



The production of 21 or 23 grms. of slime shows that the 

 medium contained a sufficiency of asparagine and salts, and the 

 yield of 8 grms. with 1% levulose and 15 grms. with 2% shows 

 a depression such as might be caused by the presence in the 

 medium as prepared of about 1% of dextrose (see p. 231). The 

 depressing constituent of the potato- juice might have been held 

 accountable for the non-production of slime from saccharose had 

 it not been discovered towards the close of this research that the 

 bacteria could again utilise the sugar. The power of forming 

 slime from saccharose was thus a faculty which the organism could 

 gain and lose, and to maintain this power it had to be rapidly 

 subcultivated upon saccharose media, that is, the transfers had 

 to be made every second or third day. Upon referring to my 

 notes I found that, subsequent to the work connected with the 

 first two papers of this series, the bacteria had been subcultivated 

 upon ordinary nutrient agar which contains no saccharose. 

 From the beginning of this research I had grown them upon 

 saccharose-potato-agar, and on this medium the power of using 

 saccharose had been regained. 



Slime from molasses. — Bearing in mind the possibility of arabin 

 being in the future manufactured industrially from certain waste 



Potato-juice 10, tannin 01, agar 2, water 90 grms. 



