POISONOUS DRUGS 177 
for their power upon certain volatile oils, camphors, resins, 
alkaloids, and some other classes of compounds which 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 poisons 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 say 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 C,.H,,O. 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 and display curious 
animal-like movements due to the liberation of camphor 
vapor. The movement is checked by 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. 
1 An antiseptic is a substance which is poisonous to the microscopic 
germs, or septic organisms as they are called, which cause fermentation, 
putrefaction, and certain diseases. | 
