Chapter II: Their Formation Into Masses

This is a subject of far greater importance than is usually assigned to it, as will be more fully explained in the sequel.

1. Many substances, as _vegetable extracts_, may be formed into pills without any addition; others, as _gum resins_, become sufficiently soft by being beaten, or by the addition of a drop or two of spirit, or _liquor potassæ_. Some dry substances react upon each other, and produce, without the addition of any foreign matter, soft and appropriate masses. The _Pilulæ Ferri Compositæ_, of our Pharmacopœia afford a very striking example of this peculiar change of consistence, which the mutual reaction of the ingredients produces by simple triture. The _Pilulæ Aloes Compositæ_ offer another instance; for the extract of gentian, upon being triturated with aloes, produces a very soft mass, so that the addition of a syrup, as directed by the Pharmacopœia, is quite unnecessary. See _Form: 12_.

2. Many substances are, in themselves, so untractable, that the addition of some matter foreign to the active ingredients, is absolutely essential for imparting convenience of form. It is generally considered that very little skill and judgment is required in the selection of such a substance, provided it can fulfil the _mechanical_ intention just alluded to—the fact however is, that _the medicinal power of the pill may be materially controlled, modified, or even subverted, by the mode in which it is formed into a mass_. Where the active element of a pill is likely to be improved by minute division, a gummy or resinous constituent may be usefully selected: under the history of Aloes, I have alluded to a popular pill, known by the name of the _dinner-pill_, in which case the _mastiche_ divides the particles of the aloes, and modifies the solubility of the mass. The _Pilulæ Opii_ of the former Pharmacopœia of London, consisted of equal proportions of opium and extract of liquorice, and the mass was so insoluble that its effects were extremely uncertain and precarious; in the present edition, soap has been very judiciously substituted; but in certain cases where we wish to protract the influence of opium, or that of any other active body, so as not to obtain its full effects at once, we may very advantageously modify its solubility by combining it with a gum resin or some substance which will have the effect of retarding its solution in the stomach. The _Pilulæ Styrace_ of the Dublin college, presents itself as an efficient example of this species of pharmaceutical address; see also _Form. 10, 11, 12_. I am well acquainted with many formulæ whose utility has been sanctioned by experience, and I have no hesitation in believing that their salutary mode of operation would receive a plausible explanation from this simple law of combination. Dr. Young has very justly stated in his Medical Literature,[297] that the _balsam of copaiba_ envelopes metallic salts, so as to lessen their activity; he says that the sub-carbonate of iron, made into pills with copaiba, was given for some weeks without any apparent effect; and that a few hours after the same quantity had been given, with gum only, the fæces were perfectly black. I do not know a more striking and instructive proof of the influence of a glutinous or viscid constituent, in wrapping up a metallic salt, and defending the stomach from its action, than is presented in the case published by the medical attendant Mr. Marshall, in consequence of the attempt of Eliz. Fenning to poison the family of Mr. Turner of Chancery-lane by arsenic, which she providentially administered in a heavy yeast dumpling. _Soap_ is very frequently used for the formation of pill-masses, and it is an excellent constituent for substances likely to be injured by meeting with an acid in the _primæ viæ_; many resinous bodies may also be reduced to a proper consistence 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]

_Water_ will on some occasions be found a convenient expedient; powdered _Rhubarb_ or _Jalap_ may be thus made into masses without any increase of bulk, but the pills will be apt, if kept, to become mouldy.

3. In the formation of pills the ingredients should be hastily rubbed together, whenever they are liable to be injured by long exposure to the air; thus in the formation of _Pilulæ Hydrargyri submuriatis compositæ_, the compound is rendered less active by too long continued triture. See _Pulveres_.

4. In dividing pill-masses, it is usual to add to them, and envelope them in, magnesia; where calomel is present, I have satisfied myself by experiment that a _muriate of magnesia_ is formed under such circumstances, and it is owing to this partial decomposition, that the surface of the pill exhibits a greenish hue; starch, powder of liquorice,[299] or orrice root, might perhaps under such circumstances be more judiciously preferred. In Germany, the powder of _Lycopodium_ is generally used. Formerly, the pill was covered with gold leaf, which protected it from the influence of the stomach, and frequently rendered it unavailing.

It has been observed that many of the pill-masses directed in our Pharmacopœias, are liable to become so hard[300] and dry by being kept, that they are unfit for that division for which they were originally intended; indeed Dr. Powel considers it doubtful whether the greater number of articles had not better be kept in powder, and their application to the formation of pills left to extemporaneous direction; the necessity of this is farther apparent, when we learn that it is a common practice for the dispenser to soften these masses by the application of a hot spatula, or pestle, which sometimes carbonizes, and frequently decomposes them.