156 BEVERAGES. 



The nutritious value of fruits is not to be overlooked. When 

 fresh and ripe they are easily digested, and serve besides a useful 

 purpose in keeping the bowels in regular action. 



BEVERAGES. 



Under this general head are included tea, coffee, cocoa, and 

 alcoholic beverages. Some of these have a distinct food-value, 

 others are stimulants only, while the opinions held by authorities 

 as to some of the others are so diverse and the results of experi- 

 ments so differently interpreted, that it is difficult with our present 

 knowledge to classify them with precision. 



Tea. Tea is an infusion made from the leaves or leaf-buds 

 of the tea plant, the principal constituents of which are an aro- 

 matic oil, an alkaloid, thein (C 8 H 10 N 4 O 2 ) 1.8 per cent., tannin 

 about 15 per cent., albuminous compounds, dextrin, and salts con- 

 taining potash and phosphoric acid. Tea is a stimulant by virtue 

 of the thein which it contains, and an astringent because of the 

 presence of tannin. 



Tea should be made with boiling water, and in about five 

 minutes the infusion should be poured into another vessel ; if left 

 longer, it becomes bitter and unwholesome because of the large 

 amount of tannin dissolved. 



Coffee. This beverage is an infusion made from the seeds 

 of the coffee plant. The seeds or berries contain fat, legumin or 

 vegetable casein, sugar, dextrin, salts, an aromatic oil, and an alka- 

 loid caffein (C 8 H 10 N 4 O 2 ) about 0.75 per cent., and caffeo-tannic 

 or caffeic acid, a variety of tannic acid. Thein and caffein are 

 isomeric, and their effects are similar. While tea is astringent, 

 coffee has a laxative action on the bowels and acts as a stomachic 

 tonic. 



It has also been claimed that both tea and coffee act indirectly 

 as foods by retarding the waste of the tissues ; whether this is true 

 or not, they certainly have their uses in removing the sense of 

 fatigue, and they also allay the sensation of hunger. If used to 

 excess, however, both coffee and tea disturb the digestive organs 

 and produce nervous disturbances, such as headache, trembling, 

 and wakefulness. This condition is most commonly observed in 

 the confirmed tea-drinker, who is as intemperate as anyone addicted 

 to the excessive use of alcohol. Black coffee increases the heart 

 action, and is given by physicians when the circulation is depressed. 

 It is also given in cases of poisoning by opium. For its relation 

 to uric acid see page 434. 



Cocoa. This is prepared from the seeds of Theobroma cacao, 

 which are roasted, husked, and crushed. Cocoa-nibs, as the 

 crushed seeds are called, contain about 50 per cent, of oil or cocoa- 

 butter, 15 per cent, of proteids, and an alkaloid, theobromin, 0.5 



