TEA. 



119 



effects upon the system are similar to those of coffee, but are 

 generally not so marked. Ordinary tea, taken in moderate 

 quantity, like coffee, relieves fatigue and increases mental 

 activity, but does not usually induce such persistent wake- 

 fulness. 



It is unnecessary to describe all the varieties of tea in com- 

 mon use. There are, however, certain .varieties, called green 

 teas, which present important differences, as regards compo- 

 sition and physiological effects, from the black teas, which 

 are more commonly used. The following is a comparative 

 analysis of these two varieties by Mulder : 1 



Composition of Tea. 



Both tea and coffee possess peculiar organic principles. 

 The active principle of tea is called theine, and the active prin- 

 ciple of coffee, caffeine. These have been found to be iden- 

 tical in ultimate composition ; their formula being C 8 H 5 O 2 ]^" 2 . 

 As they are supposed to be particularly active in producing 



1 PEREIRA, Food and Diet, New York, 1843, p. 190. 



Hyson is a green tea, and Congou is black. With regard to the proportion 

 of theine in teas, there is considerable difference of opinion. Payen (op. dt., p. 

 427) quotes the analyses of Peligot, which give from 2-34 to 3 parts per 100. He 

 also found from 20 to 30 per cent, of nitrogenized matter. 



a A pecuh'ar brown deposit which slowly takes place in vegetable extracts 

 (Berzelius). 



