284 VOLATILE OIL, GUM, TANNIN. 



flavour as when the other principles were retained ; 

 so that the flavour of roasted coffee must be 

 ascribed to the joint effect upon all the consti- 

 tuents." 



In fact Mulder, though he considers the odorous 

 principle of tea dependent on a volatile oil, never- 

 theless states, that the properties of tea are best 

 ascertained from the four principal constituents 

 already named. 



The volatile oil of tea Mulder considers of a 

 highly poisonous character, and difficult to ob- 

 tain : it possesses the flavour of tea in a high de- 

 gree, and in contact with the tongue causes a strong 

 taste of tea in the mouth, without astringency.* 



To the astringent principle, however, he attaches 

 even more importance than to the essential oil. 

 He describes it as refreshing in the mouth, and 

 states that analysis and price both show that teas 

 are of superior or inferior quality in proportion to 

 the quantity of tannin they contain. 



Gum, agreeably to this Author, also plays a very 



* Mr. Jacobson. states, that a single drop of the juice ex- 

 pressed from the fresh leaves of inferior shrubs growing in low 

 clay grounds 2000 feet above the sea produces nausea ; but 

 that obtained from leaves of finer quality grown 4000 feet above 

 the sea in rich, brown, and particularly black ground (consist- 

 ing of decayed vegetable matter), may also be termed nauseous, 

 though in fact it is only harsh, and astringent in the throat, 

 and at length becomes sweet. {Handboek v. d. Kidlaur en 

 Fdbrikatie v. Thee, § 463.) 



