8 Introduction [CH. I 
meadow occupied by the plaintiff. In Pouting v. Noakes (63 L. J. B. 
549 ; (1894) 2 Q.B., 281) the defendant was not held liable for the death 
of a horse which ate off the branches of a yew tree, because the tree did 
not extend up to or over the plaintiff's boundary, though it overhung 
a ditch, the edge of which was the boundary, and was hence accessible 
to the plaintiff's stock. 
The Toxic Principles of Plants. The poisonous substances in 
plants may be grouped either (1) according to their physiological effects 
on certain organs ; (2) according to the principal outward and perceptible 
symptoms caused ; or (3) in accordance with their chemical relationships. 
In regard to (1) the poisons may be nerve, heart, blood-poisons, etc. 
(2) The poisons may be acrid, narcotic, or both. Acrid poisons are those 
which cause irritation or inflammation of the digestive tract (Euphorbia, 
Ranunculus, Daphne, etc.}', narcotic poisons affect only or chiefly the 
brain (Agrostemma, Papaver, Atropa) or chiefly the spinal cord (Clavi- 
ceps purpurea, Lolium temulentum) ; acrid-narcotic poisons induce to 
a greater or less extent the symptoms of both the foregoing groups 
(Taxus, Colchicum, Cicuta, Solanum, etc.). 
(3) As the accounts of the individual plants will show, the toxic 
principles of many plants are not yet well understood, either as regards 
chemical constitution or symptoms caused. Many poisons may be driven 
off by heat (boiling, drying), and some plants may thus be rendered 
harmless. 
Most of the toxic principles of our native poisonous plants are 
Alkaloids or Glucosides. The former all contain nitrogen, differ con- 
siderably in molecular constitution, and are usually combined with 
widely distributed organic acids. In the pure state they are colourless 
and usually stable, crystalline or amorphous solids, or readily volatile 
liquids ; they usually have a burning taste. In general the same base is 
confined to species of the same order e.g. Solanine to the Solanacece. 
The alkaloids include the most powerful poisons. 
The term "Glucoside" indicates a group of substances which by 
the action of an acid or enzyme are split up into a sugar (grape sugar, 
galactose or rhamnose) and other substances (alcohol, aldehydes, acids). 
They have a bitter taste and are generally readily soluble in water. 
Related to the glucosides are also the Saponins, remarkable for the 
fact that they induce an exceedingly frothy condition in water; the 
prussic acid yielding compounds or cyanogenetic glucosides (e.g. 
Amygdalin and Phaseolunatin) also belong to this group. Other 
substances will be mentioned in the succeeding chapters. 
