FERMENTS, FERMENTATIONS, AND LIFE. 269 



within it fermentation of the sugar, that is to say, the 

 formation of a little alcohol ; and this in its turn is sus- 

 ceptible of the passage into acetic fermentation, giving the 

 pulp an acid taste. At last the pulp itself is destroyed by 

 various fungous growths. When a fruit decays and takes 

 a more or less unpleasant flavor, this depends on the in- 

 tervention of ferment-cells of atmospheric origin, and on 

 the production of acid or alcoholic substances. An able 

 micrographist, Engel, who has lately studied these phe- 

 nomena minutely, discovers that the yeast-cells which thus 

 produce alcoholic fermentation in the juices of fruits present 

 some slight differences in various fruits, neither do they 

 have the same morphological character as those of grape- 

 must or beer-wort. Varieties occur in these cases, corre- 

 sponding to the different media in which the nutrition of 

 the little fungus takes place. 



The microscopic fungi of the atmosphere play as in- 

 teresting a part in-the alteration of wines. These grow 

 acid, change, become filmy or oily, or take on besides a 

 decided bitterness. All these sicknesses depend on the 

 development of different little plants recognized and de- 

 scribed by Pasteur ; and this scientist, not stopping at the 

 solution of the nature of these disorders, has sought the 

 means of preventing them. Resting on some former ob- 

 servations by D'Appert, he conceived the idea of subject- 

 ing wines to the action of a very high degree of heat, so as 

 to destroy the yeast-germs. There was no possibility of 

 doubt as to the destruction of these germs and the preven- 

 tion of any further change, but it might well be asked wheth- 

 er the delicacy and bouquet of certain wines would not 

 be endangered by the effects of heating. Long-continued 

 experiments prove not only that heating is an excellent 

 method of preventing sickness in wines, but also that, in- 

 stead of impairing their exquisite qualities, it ripens and 

 strengthens them. The recorded minutes of tastings of. 



