4 STUDIES ON FERMENTATION. 



diseases of wine, at the commencement of its manufacture, 

 show themselves, so to say, in a latent state only. Therefore 

 a vintage can be left, without inconvenience, to spontaneous 

 fermentation. 



With wort the case is quite diflferent. Under certain 

 accidental circumstances it is possible that alcoholic fermenta- 

 tion alone may take place in a wort left to ferment spontaneously, 

 and the quality of the beer remain unimpaired, but such an 

 event would be exceptional, and of very rare occurrence. In 

 most cases we should obtain an acid or putrid liquid resulting 

 from the production and multiplication of alien ferments. 



The addition of yeast is made in consequence of the necessity 

 of exciting through the whole bulk of wort, as soon as it is 

 cold, a single fermentation — viz., the alcoholic, the only one 

 that can produce beer properly so called. 



The alcoholic ferments concerned in the production of beer 

 will be found represented in several of the engravings in this 

 work. Other ferments we may term " diseased " ; these include 

 all those that may occur spontaneously — that is, whose germs 

 have not been directly and intentionally introduced — amongst 

 the actual alcoholic ferments. 



The expression, " diseased ferments," is justified by the cir- 

 cumstance that the propagation of these ferments is always 

 accompanied by the production of substances which are acid, 

 putrid, viscous, bitter, or otherwise unpalatable, a consideration 

 of commercial rather than scientific importance. From a physio- 

 logical point of view, all these ferments are of equal interest 

 and importance. The botanist, as a man of science, in contem- 

 plating nature, must give equal attention to all plants, whether 

 useful or noxious, since they are all governed by the same 

 natural laws, among which no order of merit could be estab- 

 lished. The exigencies of industry and health require, however, 

 wide distinctions. 



The first engraving (Plate I.) represents the difierent diseased 

 ferments, together with some cells of alcoholic yeast, to show 

 the relative size of these organisms. 



