122 BACTEKIAL ORIGIN OF GUMS OF ARABIN GROUP, 



During the feriiientatioii of saccharose, carbon dioxide is 

 evolved. This was proved by connecting flasks of baryta water 

 with small cultures of the organisms in saccharose-potato extract. 

 The usual precautions were adopted to seal the air inlet and trap 

 the air outlet with a tube containing soda-lime. Upon drawing 

 the air in the culture flask through the baryta water, barium 

 carbonate was formed. 



To gain some idea as to the relative quantities of volatile and 

 non-volatile acids, a test was made with the acids obtained after 

 extracting the sulphuric acid solution and the calcium sulphate 

 residue of Bact. nietarahiniini with ether. These were added 

 together, after filtering ofi" the insoluble fatty acid, and distilled 

 in a current of steam until the distillate had but a faint acidity. 

 The non-volatile acids were maintained at 50 c.c. and the distillate 

 measured 600 c.c. The volatile acids required 19 c.c, and the 

 non-volatile acids required 59 c.c. of normal soda'for neutralisa" 

 tion. The proportion is therefore, roughly, three parts of non- 

 volatile to one of volatile acids. 



In summarising these results it is seen that the acids formed 

 by the action of Bact. acacue, and Bact. met m- ah it mm upon 

 saccharose, with asparagine as a nitrogenous nutrient, consist of 

 about three parts of non-volatile and one part of volatile acids. 

 The former corisistof laevolactic, chiefly, with a smaller quantity 

 of succinic, of lauric and traces of oxalic. The volatile acids 

 consist of acetic, chiefly, with a smaller quantity of formic and 

 carbon dioxide. Ethyl alcohol is also formed during the fermen- 

 tation. 



IV. — The Gum-flux of the Vine. 



The disease of the vine which is known by the name of 

 " gummosis " or " mal nero," is characterised by the stems 

 becoming stunted, the young branches do not develop normally, 

 and the green leaves become deformed. Cross sections of the 

 stem show the wood speckled with black in the earlier stages of 

 the disease, and in the later stages the whole section is of a dark 

 brown colour. Tlie disease begins at the growing points^ 



