Dr. Thomson on the Vinegar Plant. 239 



times smaller than those of yeast. This pellicle becomes thicker, more 

 compact, and coherent, and in fourteen days it begins to grow on the 

 exterior border. It then presents the aspect of a chcetophora — a gela- 

 tinous, fucoid appearance. 



To endeavour to throw some light upon the mode of action of the 

 vinegar plant, I inserted a portion of a plant, well washed with distilled 

 water, in a solution of sugar, and exposed the whole to the influence of 

 the air. The liquid, when first formed, had no action on litmus paper, 

 but in a few days it was characterized by a distinct acid reaction. After 

 some weeks I took a portion of the fluid, saturated it with carbonate of 

 soda, and distilled it in a glass retort. A liquid passed over which pos- 

 sessed the odour of alcohol, and which gave aldehyde and green oxide 

 of chromium when treated with bichromate of potash and sulphuric acid, 

 according to a mode of testing which I described some years ago. (Proc. 

 Phil. Soc. Glas., ii. 94.) After two-thirds of the fluid in the retort 

 was distilled, the receiver was changed, and sulphuric acid was poured into 

 the retort, heat being applied cautiously. An acid liquid passed over 

 into the receiver, which possessed the odour of vinegar, and rendered 

 yellow a colourless solution of sesquichloride of iron. It was therefore 

 acetic acid. Another experiment was made to determine the natiu-e 

 of the products of the vinegar plant, in the absence of oxygen. An ounce 

 of sugar was dissolved in twenty ounces of water, a vinegar plant was 

 introduced into the solution, the bottle was stopped close with a ground 

 stopper, carefully waxed, and inverted in a glass full of distilled water. 

 After some weeks, only a small portion of fluid was found in the bottle, 

 smelling strongly of alcohol, and yielding aldehyd and green oxide of 

 chromium to bichromate of potash and sulphuric acid. The stopper was 

 still fixed in the bottle, but the wax had given way in one place by the 

 pressure of the gas, so as to allow of the expulsion of the fluid into the 

 exterior vessel filled with water. The greater portion of the | bottle 

 was filled with a gas, which upon examination was found to precipitate 

 lime water abundantly, and to be absorbed by caustic soda. It was, 

 therefore, carbonic acid. 



Formalion of Alcoliol. — From these experiments it seems undoubted 

 that the vinegar plant possesses the j)owcr of breaking up sugar in its 

 solutions into alcohol and carbonic acid, and as the plant during the 

 process appears to be increasing in bulk, it seems scarcely legitimate to 

 ascribe the decomposition of the sugar to any process of decay in the 

 plant itself. I am not prepared from my own observation to state that, 

 in absence of air, the vinegar plant when immersed in a solution of sugar, 

 does increase in bulk, or, in other words, grow, although I have no reason 

 to doubt the fact. But from the observations of Scblossberger and 

 Schmidt, there can be little hesitation in concluding that the vinegar 

 plant is merely a modification of the yeast globules, and therefore that 

 it is capaiiJo of augmenting in size under the same conditions as the 

 latter form of vegetation. When a plant of this description is found to 



\'oi.. TIL— No. 4. 3 



