1. _Suitable Substances_ are, 1, All remedies which operate in small
doses, as _Metallic Salts_; and 2, Those which are designed to act
slowly and gradually, as certain _Alterative Medicines_, or 3, which are
too easily soluble when exhibited in other forms, as _Gamboge_, &c. 4,
Substances which are not intended to act until they reach the larger
intestines, as in pills for habitual costiveness; _see Aloes_. 5, Bodies
whose specific gravities are too considerable to allow their suspension
in aqueous vehicles. _Efflorescent_ salts may also be exhibited in this
form, but they ought to be first deprived of their water of
crystallization, or the pills composed of them will crumble into powder
as they dry.
2. _Unsuitable Substances_ are, 1, Those which operate only in large
doses. 2, Which deliquesce. 3, Whose consistence is such as to require a
very large proportion of dry powders to afford them a suitable tenacity,
as _oils, balsams_, &c. 4, Substances that are so extremely insoluble,
that when exhibited in a solid form they pass through the canal
unaltered, as certain _extracts_.
Many remedies which are incompatible with each other in solution, may be
combined in pills, unless indeed their medicinal powers are adverse or
inconsistent, or their divellent affinities sufficiently powerful to
overcome their state of aggregation.