, silver, and the rest, for the reasons I have
before mentioned. Even iodine, which, as it is found in certain plants,
seems less remote from the animal tissues, gives unequivocal proofs
from time to time that it is hostile to some portions of the glandular
system.

There is, of course, less prima facie objection to those agents which
consist of assimilable elements, such as are found making a part
of healthy tissues. These are divisible into three classes,--foods,
poisons, and inert, mostly because insoluble, substances. The food of
one animal or of one human being is sometimes poison to another, and
vice versa; inert substances may act mechanically, so as to produce
the effect of poisons; but this division holds exactly enough for our
purpose.

Strictly speaking, every poison consisting of assimilable elements may
be considered as unwholesome food. It is rejected by the stomach, or it
produces diarrhoea, or it causes vertigo or disturbance of the heart's
action, or some other symptom for which the subject of it would consult
the physician, if it came on from any other cause than taking it under
the name of medicine. Yet portions of this unwholesome food which
we call medicine, we have reason to believe, are assimilated; thus,
castor-oil appears to be partially digested by infants, so that they
require large doses to affect them medicinally. Even that deadliest of
poisons, hydrocyanic acid, is probably assimilated, and helps to make
living tissue, if it do not kill the patient, for the assimilable
elements which it contains, given in the separate forms of amygdalin and
emulsin, produce no disturbance, unless, as in Bernard's experiments,
they are suffered to meet in the digestive organs. A medicine consisting
of assimilable substances being then simply unwholesome food, we
understand what is meant by those cumulative effects of such remedies
often observed, as in the case of digitalis and strychnia. They are
precisely similar to the cumulative effects of a salt diet in producing
scurvy, or of spurred rye in producing dry gangrene. As the effects of
such substances are a violence to the organs, we should exercise the
same caution with regard to their use that we would exercise about
any other kind of poisonous food,--partridges at certain seasons, for
instance. Even where these poisonous kinds of food seem to be useful, we
should still regard them with great jealousy. Digitalis lowers the pulse
in febrile conditions.