symptoms of arsenic
poisoning.

The son, who was always quarrelling with the rest of the family, was
arrested on the doctor's report and charged with murder. But a
_post-mortem_ examination showed that cholera was the real cause of
death.

Apoplexy, in the same way, is very like opium poisoning; and
hydrophobia, lock-jaw, and even some cases of hysteria, closely resemble
poisoning by strychnine.

Still, when a healthy man grows suddenly ill soon after a meal, the
doctor keeps his eyes open, and if death follows he has a pretty shrewd
idea of what caused it.

At all events, he feels perfectly justified in assuming that the case is
not a normal one. He therefore hands over to the analyst the jars and
other receptacles containing the portions of the subject's body likely
to bear traces of the poison, knowing full well that if any poison is
there the analyst will infallibly detect it.

The analyst begins by making a series of what may be called "brews,"
mincing, pounding, boiling, cooling, filtering, decanting, and
distilling, over and over again. In these operations various solvents
are used in succession, plain water separating out one class of poisons,
alcohol dissolving out another group, benzol taking up a third, naphtha
a fourth, ammonia a fifth, and so on. This preliminary work takes, not
hours, but days to perform. At an early stage in it the operator
discovers such volatile poisons as prussic acid, chloroform, carbolic
acid, and phosphorus, if any of them be present. Later on he comes
across the alkaloids, such as strychnine, digitalin, cantharidin, and
other terrible poisons of that class.

Finally, the residue of the animal matter with which we have supposed
the medical detective to be experimenting is mixed with hydrochloric
acid, and distilled once again, after which it can contain no poison
except one of the metals.

Thus, in the course of his examination, the analyst has made a number of
decoctions, in one of which the poison is certain to be. In each
decoction there may be any one of several groups of poisons.

In which is it, and what is it? After all this patient labour the
solution is still far off. It may be a ptomaine from poisonous fish or
decayed meat, a deadly berry, or leaf, or root, a small quantity of
morphia, or phosphorus, or lead, or arsenic, or antimony.

Each brew is tested in turn. But, as illustrating the general procedure,
take the last, which contains whatever metal may have