STIMULANTS AND NARCOTICS 65 



II. Beverages 



79. General effect of tea and coffee on the body. — The 



effect of tea and coffee on the body is due to the presence of 

 essentially the same stimulant in both (caffein), which acts 

 largely on the nervous system. In both tea and coffee, as 

 they are usually prepared, is another substance known as 

 tannin. This chemical, when obtained from the bark of 

 certain trees, is used in tanning or hardening leather. When 

 tannin is taken into the stomach, it is found to injure the 

 mucous membrane and to retard digestion. 



80. The preparation of tea and coffee. — To prepare tea 

 properly, boiling water should be poured upon tea leaves, 

 and the infusion allowed to stand only a few minutes before 

 pouring. Tea should never be put on the stove to boil, 

 for two reasons: in the first place, by this treatment the 

 delicate taste and odor of the beverage are lost ; and in the 

 second place, if the tea infusion is boiled, a considerable 

 quantity of the tannin is dissolved by the water. Obviously 

 the tea grounds should not be used a second time. 



Most that has been said in regard to tea applies equally 

 well to coffee, except that in the preparation of coffee the in- 

 fusion should be put on the stove and allowed to come to a 

 boil ; it should then be poured out, and should not stand on 

 the coffee grounds ; otherwise the tannin will be extracted. 

 Coffee is best prepared by the use of a percolator, since in 

 this utensil the water is continuously forced over the ground 

 coffee. 



81. The use and abuse of tea and coffee. — " When 

 properly made, tea in moderation is a wholesome, agreeable, 

 and refreshing stimulant beverage, particularly grateful 

 in conditions of mental or physical weariness. Used in 



