8 Introduction [CH- i 



meadow occupied by the plaintiff. In Pontiing v. NoaUs (63 L. J. K 

 549 • (1894) 2 Q.B., 281) the defendant was not held liable for the death 

 of ahorse which ate ofE 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 plaiatiff'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, Papa/oer, 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 aU 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 

 Uquids ; 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. 

 Belated 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. 

 AmygdaUn and Phaseolunatin) also belong to this* group. Other 

 substances will be mentioned in the succeeding chapters. 



