NON-POISONOUS DRUGS 163 



The number of plants which have been used medicinally is 

 enormous. ]\Iany of these, however, have been found to be 

 either so dangerous in their action or of so little value that 

 they are now used if at all only by the ignorant. Neverthe- 

 less, the number of those still used in scientific medicine is 

 rather large. Numerous also are the poisonous plants known 

 to botanists. Plainly, in the present chapter only a small pro- 

 portion of these can be considered. The ones chosen are 

 typical examples of those classes of medicinal and poisonous 

 plants about which it is most important for a beginner to 

 know. The medicinal plants are thus divided: (a) those 

 yielding non-poisonous drugs, and (b) those yielding poisonous 

 drugs. Poisonous plants are grouped into (a) those dangerous 

 to eat and (b) those dangerous to handle. 



60. Non-poisonous drugs include various substances which 

 may be more or less nutritious, stimulating, or irritating, 

 or may be useful for their soothing influence upon inflamed 

 surfaces, or for some other mild healing virtue. Some of the 

 substances here included under this heading may perhaps 

 under extraordinary conditions act as poisons; what is meant 

 by calling them non-poisonous is that much larger quantities 

 tha,n are generally used would be required to produce any 

 harmful effects under all ordinary circumstances. 



The chemical compounds upon wdiich their value mainly 

 depends include mucilaginous or gelatinous constituents, as- 

 tringents, fixed oils, and volatile oils. Various other sub- 

 stances of more or less importance occur in certain of the non- 

 poisonous drugs but these need not concern us here, es- 

 pecially as many of them are not yet well understood by 

 chemists. 



Mucilaginous or gelatinous substances form the most im- 

 portant part of the drugs known as gum arable, tragacanth, 

 marshmallow, flaxseed, quince seed, elm bark, sassafras pith, 

 Iceland moss, Irish moss or carrageen, and licorice root. 

 Gum arable is an exudation from the trunk and branches of 

 the gum arable tree (Fig. 156) and related species. When 

 pure the gum consists essentially of a carbohydrate called 

 arabin, the formula of which is CioHo.jO,,, the same as that 

 of cane-sugar. Prolonged boiling with dilute acid converts 



