_regularity in their increase_. It is clear, however, that even this
character cannot be universal. For in all cases of slow poisoning by
repeated small doses there must be remissions and exacerbations, just as
in natural diseases. Besides, as we can seldom watch the symptoms
advancing in their simple form, but must endeavour to remove them by
remedies, remissions may thus be produced and their tendency to increase
steadily counteracted. Farther, some poisons admit of exacerbations and
remissions, even when given in one large dose; and there are others, the
very essence of whose action is to produce violent symptoms in frequent
paroxysms. Of the latter kind are nux vomica, and the other substances
that contain strychnia. Of the former kind is arsenic: in cases of
poisoning with arsenic it often happens, that after the first five or
six hours have been passed in great agony, the symptoms undergo a
striking remission for as many hours, and then return with equal or
increased violence. Still it is true that on the whole the symptoms of
poisoning are steady in their progress; so that this should always be
attended to as one of the general characters. In the case of slow
poisoning, too, when the most remarkable deviations from it are
observed, the very occurrence of exacerbations and remissions, combined
with certain points of moral proof, may furnish the strongest evidence
possible. Thus, on the trial of Miss Blandy at Oxford in 1752, for the
murder of her father, one of the strongest circumstances in proof was,
that repeatedly after she gave the deceased a bowl of gruel, suspected
to be poisoned, his illness was much increased in violence.[70]
As connected with the present subject, a question might here be noticed
that has been discussed on the occasion of various trials, namely,
whether the symptoms of poisoning are susceptible of a complete
intermission. It cannot be answered satisfactorily, however, except with
reference to particular poisons. The property alluded to has been
ascribed to several poisons, even to mercury, arsenic, and opium; but
oftener, I believe, in consequence of an improper desire on the part of
the witness to prove or to perfect their view of the case, than through
legitimate induction from facts.