108 ELEMENTARY PHYSIOLOGY. 



alcohol. Thus alcohol may be made from many sub 

 stances. The juices of all fruits contain the sugar 

 from which it may be produced. From the grape, 

 currant, blackberry, elderberry and cherry, wine 

 is made; from apples, cider is pressed; whisky is 

 made from corn, barley, rye and other grains; rum 

 is made from molasses and sugar cane. All of 

 these contain alcohol in different quantities. 



If you take an apple and squeeze out 



Sone? 8 ^ ^ ^ ie J u ^ ce ' y u w iH have cider. 



If this is allowed to stand in the 

 warm open air, it will very soon begin to change its 

 nature. If watched closely, small bubbles will be 

 seen rising to the top and escaping. These are bub- 

 bles of carbonic acid gas, one of the products of the 

 change of the fruit-sugar. The other is alcohol, 

 which mixes with the liquid. The cider is now no 

 longer sweet, but contains alcohol, is properly called 

 "hard cider," and is a dangerous drink. It is 

 the escaping gas that makes cider sparkle, and 

 beer foam. 



The change of the cider, from sweet to 

 Fermentation -hard, or from the harmless juice of the 

 apple to that containing alcohol, is called fermenta- 

 tion. All alcohol is the result of the fermentation 

 of sugar, or some substance containing sugar. The 

 apple juice, as soon as exposed to the warm atmos- 

 phere, absorbs from the air a peculiar substance 

 called a ferment, which is something like yeast. It 



