POISONOUS DRUGS 177 



for their power upon certain volatile oils, camphors, resins, 

 alkaloids, and some otlier classes of compounds ^vhich we 

 shall not need to discuss. 



A considerable number of the medicinal plants containing 

 poisonous volatile oils we have already considered under the 

 head of food-adjuncts. Cinnamon, wintergreen, clove, 

 peppermint, spearmint, thyme, nutmeg, horseradish, mus- 

 tard, allspice, and black pepper, will be recalled as examples 

 of more or less powerful iDoisons which nevertheless in very 

 small amount are grateful and often beneficial additions to 

 our food. They are used in medicine partly for their attrac- 

 tive flavor, partly for their stimulating or irritating effect, 

 and partly as antiseptics. ^ 



Camphors are volatile substances, which form crystals at 

 ordinary temperatures. They bear much the same relation 

 to volatile oils that fats do to fixed oils, that is to saj^ they 

 are volatile oils of comparatively high melting-point. By 

 camphor is most commonly understood the gum-like drug 

 obtained by distillation from the wood of the camphor-tree 

 (Fig. 169). This drug is conveniently distinguished as laurel 

 camphor or laurinol. Its chemical formula is CioHioO. The 

 volatile nature of laurinol is prettily exhibited by gently 

 heating a little piece in the bottom of a glass tube held ob- 

 liquely so that the vapor as it rises will come in contact with 

 the cool glass at the upper end. Here will be formed snow- 

 like crystals as the vapor condenses. Similar crystals may 

 be noticed at the upper part of bottles in which camphor 

 has been kept for some time. If small bits of laurel camphor 

 be placed upon the surface of pure water contained in a per- 

 fectly clean vessel the fragments will float antl display curious 

 animal-like movements due to the liberation of camphor 

 vapor. The movement is checked bjr the presence of even a 

 slight trace of oil. Laurel camphor has many important uses 

 which need not here be mentioned. It should be remem- 

 bered, however, that taken internally it is a powerful poison, 

 ten grains (about 0.65 grams) having proved fatal to a child. 



' An antiseptic is a substance which is poisonous to the microscopic 

 germs, or septic organisms as they arc called, which cause fermentation, 

 putrefaction, and certain diseases. 



