igo6.] Alcoholic Fermentation in Cider. 



243 



method by which a series of soap bubbles can be produced and 

 blown from a single bubble, each one separating itself off when 

 it reaches a certain size. It occurs when the conditions are 

 favourable for growth. Its rapidity is remarkable ; under 

 favourable circumstances several thousand new plants can be 

 formed in twenty-four hours, starting originally with a single- 

 cell only. When conditions arc unfavourable for growth, a 

 different method of reproduction is frequently made use of. 

 This consists in the living matter or "protoplasm" of the cell 

 dividing up into a few small rounded masses inside the wall of 

 the original cell, while around each of these bodies or spores a 

 new wall is formed. When favourable conditions for growth 

 occur again, the old wall splits open and sets free the spores, 

 which swell up and begin to grow, producing new plants by 

 budding. The spores may be compared to the seeds of 

 ordinary plants, while the budding may be compared to the 

 way in which plants are propagated by buds, grafts or cuttings. 

 These spores possess considerable powers of withstanding heat 

 and cold, which the ordinary type of cell does not possess to 

 anything like the same extent. The accompanying figures 

 show the methods of multiplication of the yeast plant by 

 budding and by spore formation. 



The rapidity of multiplication depends on the extent to 

 which the conditions of growth are favourable. The most 

 important conditions, as with ordinary plants, are the nature 

 and amount of the food supply and the temperature. 



Assuming for the present purposes that apple juice possesses 

 the necessary qualities for the multiplication of the yeast plants, 

 the consideration of the action of these on the juice can be 

 proceeded with. 



When yeast plants grow in a liquid containing sugar, they 

 probably first manufacture a certain substance which possesses 

 the property of converting the sugar into other substances, 

 mainly into alcohol and carbonic acid gas. The sugar in the 

 liquid must thus gradually disappear and the sweetness be lost 

 while alcohol is formed in its place and carbonic acid gas is 

 given off from the liquid in the form of small gas bubbles. 

 This, then, is the change which occurs in apple juice during the 

 course of fermentation. The yeasts find their way into the 



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