CHAPTER V 

 MEDICINAL AND POISONOUS PLANTS 



59. Medicines and poisons. It is an old sayino- that 

 medicines are substances which make the sick well and the 

 well sick. This saying expresses in a way the truth that 

 among medicines are included some of the most powerful 

 poisons known. In fact, most medicines are poisonous, and 

 most poisons medicinal. Experience has shown also that 

 when a fatal dose of a certain poison has been taken, life 

 may sometimes be saved by giving, as an antidote, some other 

 poison in quantity sufficient even to cause death if the first 

 poison had not already been taken. 



From these facts it appears that no line of separation can 

 be drawn between medicines and poisons. By a medicine 

 we mean any substance used for the cure or relief of disease; 

 and by a poison, any substance capable of injuring the body 

 by other than mechanical means so as to cause death or 

 serious harm if taken in undue quantity. Even too much 

 food may be harmful or perhaps fatal, and the same is true 

 of the most harmless medicines, but in these cases the bad 

 effect is so largely the mechanical result of excessive quantity 

 that we do not say poisoning has taken place. Foods are 

 sometimes used as medicines, as, for example, olive-oil and 

 Irish moss. The same is true of food-adjuncts in general, 

 and, as we have alread}^ seen, many of these if taken in more 

 than small amount are poisonous. We may recall also the 

 fact that certain foods, such as tapioca, are obtained from 

 plants which contain deadly poisons. Similarly the tubers 

 of the white potato when young or when green in color, 

 contain a powerful })oison. Thus it is plain, that edible, 

 medicinal, and poisonous plants must not be thought of as 

 entirely separate and distinct classes, but merely as groups 

 made for practical convenience. 



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