220 



KNOWLEDGE. 



June, 1911. 



The exact part playt-d by the bacteria in this 

 process is still obscure, and it has not yet been 

 ascertained whether the bacteria consume the 

 alcohol and excrete it as aldehvde and acetic acid. 

 or whether they contain an enz\ inc. the function of 

 which is to act, as platinum black can do (possibly 



Figure 4. 

 Vinegar Fields in the year ISOO. Drawing off the Vint 



bv setting up suitable vibrations in the alcohol), as a 

 carrier between the o.xygen and the alcohol. 



The isolation of the enzyme, zyiiuisc. from \east. 

 and the proof that even in the form of a dr\- powder 



dcdhol, led to repeated 



it could ferment sugar int 



efforts to isolate an analogous oxidising enz\me from 



acetic bacteria : but, as yet, all such attempts to 



express from the ruptured cells a liquid which after 



filtration should produce the effect of the living 



bacteria, have ended in failure. Several species of 



acetic bacteria have been isolated. 



differing from one another in their 



form, in tlie temperatures at whicli 



the\- work best, and in the nature 



of the products that they yielti. 



()f these the best known are thr 



three species first studied in 1894 



by Hansen and shown in the 



accompan\ing illustrations. (Ser 



Figures 1 . 2 and .S.) 



All are cliaracterised by thi 

 different in\-olution forms which 

 thev assume when culti\ated upon 

 a suitable medium, under different 

 conditions. In each case when 

 grown iip(.>n the surface of a 

 nutrient liijuid, such as wort, at 

 a temperature of about .54" C. 

 (9.5" P.), the\' form pellicles upon 

 the surface, but the skin thus 

 produced differs m apjiearance. 

 that of B. act'ti being moist. 

 smooth, and >lini\'. while that ol 

 B. pastoriainim is dr\", and has a 

 corrugated surface. 



In the case of B. Kiitziu^uimini 

 the cells are. as a rule, isolated, and the forma- 

 tion of chains rarel\- occiu's. whereas the occur- 

 rence of separate cells is the exception in the 

 case of the other two species. The cells of 

 B. dCL'ti are narrower than those of the others, 

 and nut infrequentK' show a form reseml)ling a 



figure-of-eight, as was first noticed Iw' Pasteur. 

 The pellicle or skin formed by all these bacteria is 

 \\ hat is termed a zoogloeal form, and consists of the 

 cells united together into a tnass by the swelling and 

 fusion together of the outside cellular membranes. 

 PopularK- it is known as motlier-of-viiie}iai\ and 

 its excessive development in the 

 worts is an indication that in- 

 sufficient air is being supplied to 

 the bacteria. 



The apparatus in which origin- 

 all}- this acetic fermentation was 

 effected consisted of nothing more 

 than barrels filled with wood shav- 

 ings, through which the wt.irt. after 

 being mixed with a little finished 

 vinegar containing the acetic bac- 

 teria, was allowed to trickle. 

 Hundreds of these casks were 

 ranged abo\(.' [)ipes communicating 

 with the gyle store vats, and were filled by means 

 of a flexible hose connected with the pipe. Each 

 day the bungs were uncovered, if the weather was 

 fine, in order to admit a 'fresh supply of air to the 

 interior of the cask, this process being continued for 

 many weeks until the acetification was complete. 



The accompan\-ing illustration (see Figure 4) 

 represents a portion of the largest of these vinegar 



fields (those of Messrs. Beaufoy & Co.) at 

 beginning of the nineteenth century. 



the 



\ " Sendiii.n-oiit " W.irehouse. 



Ill, I klv 5. 

 Beaufov's Vinos 



;r Warehouse in the ve.ir IHOO. 



.\s these fields necessarily covered a very large 

 area the}- were obviously little suited for places where 

 land was valuable, .\part from that, fielding, as it 

 was termed, was a ver\- slow process of acetification, 



and involved heavy wastage. 



Hence, when. 



1823, Schiitzenbach devised 



