These may contain, with the exception of gum, all the ingredients contained in watery extracts, besides resin; their composition however will greatly depend upon the strength of the spirit employed as the solvent; but of this I shall speak more fully under the article Tincture.
Extractum Cinchonæ Resinosum. L.E.D. The operation of spirit in this preparation is two-fold; it extracts from the bark the element which is insoluble in water, and it diminishes the tendency in the extractive matter to absorb oxygen during the process. Dose, grs. x to xxx. It is said that a spurious extract of bark is to be met with in the market, consisting of the extract of the horse-chesnut tree bark, and yellow resin.
Extractum Colocynthidis compositum. L.D. Extract. Catharticum. P.L. 1775. Pilulæ Rudii. P.L. 1720. This preparation has been established through successive pharmacopœias, and has undergone some modification in each; in the present edition the soap has been restored, and its solubility is thereby increased, as well as its mildness as a cathartic. The omission of this ingredient was formerly suggested by the consideration of its being incompatible with Calomel; this however is not the case. It presents a combination of purgative substances which is highly judicious, and will be found to be more powerful than an equivalent dose of any one of the ingredients. Dose, gr. v to ʒss, Form. 71, 81, 88.
Extractum Jalapæ. L.E.D. It is purgative, but is liable to gripe, unless it be triturated with sugar and almonds, or mucilage, so as to form an emulsion. Dose, grs. x to ℈j.
Extractum Rhei. L. The powers of the Rhubarb are considerably impaired in this extract. Dose, grs. x to ʒss. Form. 78.
3. Inspissated Juices.
These preparations are obtained by expressing the juices from fresh plants, and evaporating them in a water-bath; they are generally of a lighter colour than common extracts, and they are certainly much more active, although there is a great difference in the activity of different samples; and perhaps the medicinal powers of the juices themselves are very much under the controul of soil and season. That they vary in quantity from such causes we have ample proof; thus in moist seasons, Beaumé obtained five pounds of inspissated juice from thirty pounds of elder berries, whereas, in dry seasons, he could rarely get more than two. From hemlock he procured in October, 1796, 7·5 per cent. of inspissated juice, and in May of the same year only 3·7; on the contrary, in August, 1768, 4 per cent., and in May, 1776, as much as 6·5; but in general, the product in the autumnal months was the most considerable.
The modes of preparing the inspissated juices of the same plant vary in the different pharmacopœias, and in several points that are very essential; some direct the expressed juices to be immediately inspissated, others allow them to undergo a slight degree of fermentation, and some defecate them, before they proceed to their inspissation.
Extractum (Succus Spissatus. E.) Aconiti. L.E. The medicinal properties of this preparation are analogous to those of the recent Wolfsbane, viz. narcotic, and in some cases diuretic, (see Form. 128.) It is however rarely used. Dose, at first, should not exceed gr. ½, but it may be gradually increased. I have not yet, says Dr. Davy, in a letter recently received from him, had much experience of the Extractum Aconiti, but that little is favourable to its use; “in some cases of chronic rheumatism, and in some of intermittent fever, complicated with visceral disease, it has had a beneficial effect not to be mistaken; the dose has been from one to two grains.” Dr. Stöerck, who first tried this medicine, observed from it a powerful diaphoretic effect; this, says Dr. Davy, “I have not noticed, and yet the extract which I have used was prepared by Mr. Barry, in vacuo, which is certainly far more powerful than that employed by Stöerck; the latter, when applied to the tongue, “levissimam tantum titillationem excitabat,” whereas that of Mr. Barry produces a most disagreeable sensation of burning, which extends to the throat; and in one instance, when applied to the tip of my tongue, it occasioned ulceration.”
Extractum Belladonnæ. L.E. See Belladonnæ Folia. Dose, gr. j, gradually increased to gr. v, in the form of pill. Dr. Davy has made a few trials of Barry’s Extract; the results of which he informs me are not at all favourable to the use of this medicine; it is much more powerful than the common extract, and can only be given with safety in small doses; “in several instances,” says he, “I have not been able to repeat a grain dose daily, more than thrice, on account of the alarming symptoms produced, as head-ache, vertigo, indistinct vision with dilated pupil, and, in one case, irritation of the bladder, occasioning very frequent micturition; in chronic rheumatism and catarrh, with severe cough, the only diseases in which I have yet given it, it has not appeared to be in the least serviceable; it may probably prove valuable to the oculist; from trials that have been made of it here by Mr. Miller, Assistant Surgeon to the Forces, it has been found to dilate the pupil beyond the common extract. Stöerck even introduced his extract into the eye with impunity. Acrid as the preparation is which I have used, the patients have never complained of it, nor have I known any disagreeable effects from it, when applied in solution, sufficiently dilute.”