by soap, although in prescribing it, its levity should be attended to, or otherwise the pills will be too bulky; in general it will combine with an equal portion of any resinous powder, as _Rhubarb_, _Jalap_, _&c._; it is of course ineligible where the substances are decomposed by alkalies, as _Tartarized Antimony_; this last precaution will also apply to _aromatic confection_ as a vehicle, on account of the carbonate of lime contained in it. The _Conserve of Roses_ has the advantage of retaining its consistency much longer than mucilage, but as it contains an uncombined acid, it is frequently inadmissible; it could not for instance be with propriety employed with the precipitated sulphuret of antimony. Pills made with mucilage, are apt to crumble when they are rolled out; this is the case with the _Pilulæ Hydrargyri submuriatis_; some extract therefore would be a more convenient constituent; in this particular case, however, the addition of a few drops of spirit would supersede the necessity of _any_ constituent. Castor oil, in some cases, especially with some of the harder purgative extracts, will impart an eligible consistence. _Crumb of bread_, furnishes a convenient vehicle for those salts which are ponderous, active in very small doses, or which are liable to be decomposed by other vehicles; but an objection is attached even to this, for it is liable to become so dry and hard when kept, that pills made with it will frequently pass undissolved. Swediaur mentions this fact with reference to Plenck’s mercurial pill, as well as to one of corrosive sublimate, and he proposes for this reason to substitute _starch_; the addition however of a small portion of sugar will prevent the bread from becoming thus indurated, and with such a precaution it may be very safely employed. For the purpose of forming active vegetable powders into pills, such as _Digitalis, Conium_, &c., I am informed by Mr. Hume of Long Acre, that in his experience _melasses_ or _treacle_ is the best constituent that can be selected, for it undergoes no decomposition by time, but maintains a proper consistency, and preserves the sensible qualities of the plant quite unimpaired for many years. I have deposited in the cabinet of the College, specimens of such pills, of _hemlock_ and _foxglove_, which retain the characteristic odour of these vegetables, notwithstanding they have been now made for several years. _Honey_ has likewise the property of preserving vegetable substances; _seeds_ may be kept in it for any length of time, some of which, on being taken out, washed, and planted, will even vegetate. It has also been used for the preservation of animal matter; the bodies of the Spartan kings, who fell at a distance in battle, were thus preserved, in order that they might be carried home.[298]