910 NEUTRAL PRINCIPLES PECULIAR TO CERTAIN PLANTS. 



water. The solution, by exposure to light, acquires a beautiful 

 blue colour, even when the quantity of esculin is very small ; 

 the blue tint vanishes with acids, but is revived by alkalies. 

 The composition of esculin is expressed by C 16 H 9 O 10 . 



PICROTOXIN. 



The substance to which cocculus indicus, the fruit of Menis- 

 permum cocculus, owes its poisonous qualities, was first investi- 

 gated by Boullay. It is obtained by boiling in alcohol the 

 bruised seeds, after depriving them, by pressure, of the greater 

 part of their fat oil, distilling off the alcohol, and dissolving the 

 remaining extract in boiling water, slightly acidulated, from 

 which the picrotoxin crystallizes on cooling. 



It forms colourless, short and thin prisms, is intensely bitter, 

 and not fusible. It is soluble in 25 parts of boiling water, and 

 very soluble in alcohol; does not combine with acids. It is 

 highly poisonous. Its composition is expressed by C 12 H 7 O 5 

 (Regnault).* 



ANTHIARIN. 



The most deadly of the Upas poisons, employed by the 

 inhabitants of the East Indian Archipelago to poison their 

 arrows, is a gum resin, from the Anthiaris toxicaria, of which 

 the active principle, anthiarim, was separated by MM. Pelletier 

 and Caventou. It crystallizes in fine white plates, which are 

 inodorous, sparingly soluble in water, more so in alcohol. It 

 acts in the highest degree as a deadly poison. Its composition 

 is C 14 H 10 5 . 



CAFFEIN. 



A crystalline substance is obtained from coffee, from tea, and 

 from guarana, a prepared mass from the fruit of Paullinia 

 sorbilis. To obtain it from coffee, the raw beans, well dried, 

 are reduced to powder, and exhausted by boiling hot water; 

 subacetate of lead is added to the infusion, to precipitate gum 

 and other matters, the liquid filtered, and the excess of lead 

 thrown down from it by sulphuretted hydrogen. After filtra- 



* Pelletier and Couerbe $ Ann.de Chim. et de Phys. liv, 181. 



