- 
2o4 PRINCIPLES OF BOTANY, ETC. 
16. Narcotic principle, which has a particular ef- 
fect on the brain, prodticing drowsiness, &c. The 
juice of the white poppy, (Papaver somniferum); of 
Hyoscyamus niger, Atropa Belladonna, Conium ma- 
culatum, Cherophyllum ¢emulum, Aethusa Cynapium, 
are instances of it. 
17. Acrid principle, which produces a pungent sen- 
sation. ‘The horse-radish, (Cochlearia armoracia); 
lemon scurvy-grass, (Cochlearea officinalis); arum, 
(Arum maculatum) ; water pepper, (Polygonum /y- 
dropiper) ; Cayenne pepper, (Capsicum annuum); 
black pepper, (Piper nigrum); foxglove, (Digitalis 
purpurea); Ranunculus acris; Aconitum Napellus, 
and many other vegetables possess it. 
18. Gallic acid. ‘This, combined with gum, is 
met with in a great number of plants, and is a very 
astringent substance. It occurs chiefly in the bark 
of trees, such as oak bark, willow, &c. 
19. Citric acid: consisting, as all vegetable acids, 
of Carbon, Hydrogen, and Oxygen, which, in each 
acid are of different proportions. This acid has 
been found in lemons, (Citrus medica); raspberries, 
(Rubus idaeus); gooseberries, (Ribes grossularia ; 
and myrtle berries, (Vacinium myrtillus). 
vomica, the poison nuts, and of Ignatia amara, the Faba febri- 
fuga, &c. This last kills all animals, and in greater quantity may 
even become noxious to men. The experiments of my friend 
Dr Hlohrman in Lund give most striking results: he killed 
with eight grains of the poison-nut a strong horse. Prof. Vi- 
bourg’s observations on the effects of the cherry laurel like- 
evise deserve attention. 
9 i 20, Mal- 
