98 MICROBES, FERMENTS, AND MOULDS. 
IV. THe MIcROBES WHICH AFFECT WINE. 
The affections to which some wines are subject 
alter their taste and quality so as often to render 
them unfit for use. These affections ought to be 
recognized, so that a diseased wine may not be con- 
founded with one which is adulterated, and it is by 
means of the microscope that we are enabled to 
recognize the nature of these changes. Chaptal for- 
merly ascribed them to the presence of an excess of 
ferment, since he was unable to discover any other 
cause. We now know from Pasteur’s valuable re- 
searches, published in his book, Etudes sur les vins, 
that they are all due to the presence of microbes 
peculiar to each disease. 
“The source of the diseases which affect wine,” 
Pasteur writes, “consists in the presence of parasitic 
microscopic plants, which are found in wine under 
conditions favourable to its development, and which 
change its nature either by the withdrawal of what 
they take for their own nutriment, or still more by 
the formation of fresh products which are due to the 
multiplication of these parasites in the wine.” These 
diseases are known under the names of acescence, 
pousse, graisse, amertume, etc. We shall review them 
in succession. 
Mouldy or Flowered Wine.—These are wines on the 
surface of which white pellicles are formed (flewrs de 
vin), which consist of Mycoderma vini (Figs. 48, 58). 
