114 



THE BACTERIAL ORIGIN OF THE GUMS OF THE 

 ARABIN GROUP. 



By R. Greig Smith, D.Sc, Macleay Bacteriologist to the 



Society. 



III. — The Acids produced during the Growth of Bact. 

 ACACiuE axd Bact. metarabi^^um in Saccharose Media. 



The two bacteria are grouped together because it became evi- 

 dent as the research proceeded that they produce identical acids. 

 The preliminary tests, which w^ere made with the view of obtain- 

 ing a general idea of the nature of the acids so that a particular 

 scheme might be adopted or devised, were made upon material 

 which had been formed in chalk solutions of saccharose-potato 

 extract. These solutions contained 5 % of chalk and 5 % of 

 saccharose. Saccharose-potato extract had, in conjunction with 

 agar and tannin, proved an excellent medium for the formation 

 of gum, and on this account it was used pending the determina- 

 tion of the essential nutrients contained in it. 



Flasks containing the media were infected with the bacteria 

 and incubated for a month at 30°. At the end of this time, the 

 cultures were evaporated, cooled, and treated with an excess of 

 dilute sulphuric acid. There were thus obtained solutions of the 

 bacterial acids and residues of calcium sulphate. The former 

 were extracted with ether in the apparatus of Schoorl,* and the 

 latter, after being dried in the air, were transferred to paper 

 cartridges and extracted by ether diffusion in the same appara- 

 tus. After treatment with ether the respective extracts were 



* Journ. Soc. Chem. Ind. xix. , 567. 



