428 OPIUM CAFFEINE. PART n. 



a species of stramonium-; and its congener tobacco, 

 now all but a necessary of life among civilized man- 

 kind, was smoked by the natives of the American con- 

 tinent, before the arrival of the Europeans, as a relief 

 from hunger. 



Coffee has been long in use on account of its sti- 

 mulating principle caffeine, which is now discovered to 

 be the same with theine, the latter, however, being less 

 exciting, unless the tea plant grows in a very hot climate. 

 In countries where nature furnishes few narcotic prin- 

 ciples, wine, beer, and spirits supply their place, especially 

 in the far north, where animal heat is rapidly carried off 

 by the cold, and carbon must be furnished to satisfy the 

 all-devouring oxygen which we draw in at every breath. 



Caffeine, the highly azotized principle of coffee, ob- 

 tained from tea leaves and coffee beans, is one of the 

 substances known as neutral crystallisable principles. 

 Similar substances are found in asparagus, pepper, 

 almonds, the bark on the roots of the apple, pear, plum, 

 and cherry trees, as well as in the bark of the willow. 

 The two last are especially analogous, and contain no 

 azote, as the others do. 



The colouring matter of flowers is a fluid contained 

 in cells, situated immediately under the skin, which itself 

 is perfectly transparent and colourless. The whiteness of 

 the white Camellia, rose, lily, and other flowers, is sup- 

 posed to be owing to the total reflection of light from 

 the cells immediately below the skin, which are either 

 full of air, or of a colourless liquid. The predominating 

 colours are yellow, red, and blue, with the various in- 

 termediate tints. Sometimes these colours are converted 

 one into another in the petal after fertilization, at 

 which period the colours are brightest. The chemical 

 nature of these liquids, the cause of their variety, and 

 their definite arrangement in one and the same petal, 

 do not seem as yet to be ascertained. 



The parts of plants that are not green inhale oxy- 



