222 BACTERIAL ORIGIN OF GUMS OF ARABIN GROUP, 



already mentioned that citrates favoured, while chlorides and 

 phosphates prevented, slime-formation upon a certain medium. 

 A small quantity, 0*12 grm., of various salts was added to 

 20 c.c. portions of medium in tubes, so that the salts were present 

 to the extent of 0*6 %. As a rule salts of potash were added, 

 but in some cases the sodium or ammonium salt chanced to be 

 the only compound in the laboratory. 



The iNFLrENCE of various Salts. 



It is seen from the table that the acid radicles may (1) 

 accelerate, (2) be indifferent, (3) depress or (4) prohibit. Succi- 

 nate and citrate favour the production of slime, and in the 

 majority of the experiments in this research one or other of 

 these salts has been employed. Tartrates are indifferent, while 

 sulphates, phosphates and oxalates are depressants. 



Among the acids which the bacterium forms from saccharose 

 are acetic, lactic and succinic. It is interesting to note that of 

 the three the first two prohibit and the last stimulates the 

 gum-forming faculty of the organism. 



Having found that citrate and succinate were stimulants, the 

 next step was to discover the optimum quantities of these salts. 

 Accordingly, tubes of media were prepared and various quantities 

 of salt added. 



' Asparagine 0-1, levulose 2, tannin 0-3, agar 2, water 100 grms. 



