3 62 THE POPULAR SCIENCE MONTHLY. 



abundantly in the leaf, though the latter, of less agreeable flavor, has 

 been little used, and is not in commerce. The use of the coffee-leaf is 

 further discouraged by the fact that the plucking of the leaf is inju- 

 rious to the crop of the berry. 



The chemist also finds theine or caffeine in two South American 

 plants, the mate and the guarana. The former, yerba mate, or " Para- 

 guay tea " {Ilex Paraguay ensis), is a small forest-tree, bearing fine 

 white floAvers, indigenous to Brazil and the Argentine Republic, where 

 it has long been prepared for a beverage which is drunk throughout 

 South America. The leaves and twigs are employed, sometimes with 

 inclusion of the fruit. Brazil also furnishes guarana, an article known 

 in medicinal commerce, and obtained from the seeds of Paulinia sor- 

 bilis, a climbing shrub. Its fruit is of the size of the grape, and has a 

 single seed. The seeds are bruised into a pulp, molded into cylindri- 

 cal cakes, and dried. So prepared, guarana is in habitual use in South 

 America, infused as a beverage, and also taken solid as an adjunct to 

 food. 



One more plant has to be named as a source of theine the tree of 

 the cola-nut, of Western Africa ( Cola acuminata). The tree, of which 

 two varieties are found, one with broad and one with narrow leaves, 

 has been cultivated somewhat in tropical countries. The nuts are of 

 the size of a pigeon's-egg, of a brownish color, a fragrant odor, and 

 aromatic, bitter taste. The natives prize them very highly, using 

 them in the solid state as a condiment with food, and to sustain strength 

 during continued exertion when the supply of food is deficient. The 

 cola-nut is rich in theine, as first shown by the analysis of Professor 

 Attfield, at London, 1864. 



So far, then, only five plants on the globe have been found to con- 

 tain the alkaloid theine or caffeine, but the chemist finds an alkaloid 

 very closely allied to this one, though of distinct individuality, namely, 

 theobromine. This interesting chemical compound is homologous 

 with the alkaloid of tea and coffee, differing in the molecule by one 

 atom of carbon and two of hydrogen, theine having the structure 

 C 8 H ]0 N 4 O 2 , and theobromine C 7 H 8 N 4 2 . The relation is the same as 

 that between any two contiguous members of the methylic alco- 

 hol series. Theine is constituted as methyl-theobromine, C 7 II 7 (CH 3 ) 

 N 4 2 , and the chemist finds it an easy task to change theobromine 

 into theine. Now, theobromine can be artificially produced from 

 xanthine (C 5 IT 4 N 4 2 ) ; indeed, theobromine is dimethyl-xanthine, 

 and theine is trimetbyl-xanthine. In other words, xanthine may be 

 presented as a chemical ancestor of the active principle of tea and 

 coffee, and so it becomes of interest to inquire into the oi'igin of 

 xanthine, so called. In reply, it must be said that xanthine is not 

 found in plants, but it is found in chemical laboratories ; it is not 

 a myth, and it can be made from a good many things that are abun- 

 dant on the face of the earth. It can be made from uric acid, and 



