The Minute Structure of the Vinegar Plant. 243 



true yeast plant, or torula, is formed in the more rapid fer- 

 mentation^ taking place at more elevated temperatures.'' 7 * 



The vinegar plant, commonly so called, is a tough, leathery 

 mass, often used by private families to make vinegar out of 

 solutions of sugar and treacle ; but the same plant exists in a 

 more delicate and diffused form when other modes of vinegar- 

 making are employed ; and M. Pasteur shows that it coats the 

 shavings, or twigs, over which some manufacturers cause a 

 suitable liquid to flow when they desire to promote its aceti- 

 fication. If a thin piece of the large, tough vinegar plant is 

 examined microscopically, a moderate power suffices to show 

 what the Micrographic Dictionary describes ; namely, an un- 

 organized jelly and cellular structures of many shapes, often 

 resembling coherent cells of yeast; others being like oidium, 

 etc., etc. It is also, in those I have examined, easy to see 

 something like an entangled mass of minute threads; but, 

 when this structure is carefully treated, myriads of bacterium 

 bodies appear, and are found to constitute the chief bulk of the 

 plant itself. 



I am. not aware that these bacterium bodies have been 

 described before, and I will therefore explain the process by 

 which I became acquainted with their existence. First a small, 

 thin strip of the vinegar plant should be torn off from any part 

 on or below the surface. This should be placed upon a glass 

 slide, moistened with a drop of water, and stretched out by 

 means of a camel-hair pencil-holder and the back of a pen- 

 knife. When reduced by stretching and squeezing to a film 

 not exceeding a 250th or a -300th of an inch thick, cover with 

 thin glass, press steadily, and view with a high power, using 

 the achromatic condenser and a small stop. An immense 

 quantity of little thread-like bodies will then be seen ; and, if 

 the power be sufficient and the illumination carefully adjusted, 

 a beaded form will appear sufficiently often to indicate the class 

 of object to which they belong. That the little bacterium 

 bodies have not been obtained by tearing- big ones to pieces in 

 the stretching process will be plain upon examination of the 

 plant in different conditions of extension and thickness. 



I have employed in this investigation Smith and Beck's 

 ^Vth and second eye-piece, giving a magnification of 1 750 lineai*, 

 with occasional resort to their first eye-piece, reducing the 

 power to 1000 linear, or to their third, bringing it up to 3000. 

 A minute drop of solution of iodine, followed by another minute 

 drop of dilute sulphuric acid, facilitates the view of the beaded 

 structure ; but it can be made out without such aid when the 

 eye has got used to the object, and the illumination is suf- 



* This theory is doubtful, as the alcoholic fermentation goes on slowly and at 

 low temperatures with the German sediment yeast. 



