CAFFEINE IN THE LEAVES OF TEA AND COFFEE. 157 



No caffeine could be detected in the authentic sample, 

 but it contained common salt, showing that it must have 

 been in contact with sea-water. I 



As T fully expected to find caffeine, and was disappointed, 

 it occurred to me that possibly the leaves of tea and coffee 

 grown at Kew might also not contain their characteristic 

 principle. 



Professor Dyer kindly supplied me with the fresh leaves 

 of several varieties and species in the middle of February. 



I found caffeine in green tea {Thea viridis) and in 

 Assam tea (T. assamica). 



The leaves of Coffea arabica, which is now fruiting, 

 contain it also, but much less in proportion than tea. 



In Coffea laurina I found a trace, but none at all in the 

 large, old leaves of Liberian coffee. 



Caffeine and theobromine occur only in the vegetable 

 kingdom. They are nearly related to uric acid, guanine, 

 and xanthin, which are products of the material exchanges 

 of the animal organism. The two former can be converted 

 into xanthin, and this, as Professor E. Fischer has shown, 

 into theobromine or methylxanthin, and into caffeine or 

 dimethylxanthin. 



As caffeine is used in medicine, it appears very probable 

 that at no distant time it will be manufactured from 

 Peruvian guano, which is the best source for guanine. 



