102 
19. It is uncertain whether ammonia or the vola- 
tile alkali exists ready formed in plants : but it is 
evolved from many of them by the action of lime 
or fixed alkali, assisted by a gentle heat ; though it 
may be always imagined to be generated during 
the process by the combination of azote and carbon . 
The ingenious researches of M. Serturner, followed 
by those of other chemists, have made us acquainted 
with the alkaline properties of several compound 
vegetable substances, which were not suspected to 
belong to this class of bodies, such as morphina, 
strvchnina, brucina, picrotoxina, delphina ; these 
compounds, which are found respectively in opium, 
nux vomica, brucaea antidysenterica, cocculus indi- 
cus, and delphinium staphysagria, agree with al- 
kalies in their effects upon vegetable colours, and 
in combining with acids, into peculiar neutro- 
saline compounds. They form the narcotic or 
poisonous principles of the plants in which they 
are found, and probably many more of them will 
be discovered. They are not very interesting to 
the agriculturist, except in this point of view, 
that possibly many noxious vegetable substances may 
be rendered usefid as the food of cattle , by extract- 
ing their noxious principles by means of acids ; 
and this is a subject well w T orthy of experimental 
investigation. 
Fixed alkali may be obtained in aqueous solution 
from most plants by burning them, and treating 
the ashes with quick-lime and water. The vege- 
table alkali, or potassa, is the common alkali in 
the vegetable kingdom. This substance, in its pure 
state, is white and semi-transparent, requiring a 
