tion. The above table contains eight columns. In the first Explana are written the scientific and corresponding pharmaceu tical names of the several simple substances, distributed into departments, according as they are taken from the vegetable or the mineral kingdom, and arranged alphabetically; in the second is written the name of the country where the article is found, or from which it is procured; in the third the part of the simple usually employed in medicine; in the fourth the form in which it is usually administered; in the fifth the dose of the simple. In the sixth column are arranged all the officinal preparations of each simple which properly belong Oleum Volatile Pimpinella Gt. 2 to 6. Croup and Anisi. Ed. Ol. Essentiale Anisi. Lond. Dub. Decoctum Polygalæ Senega. 1 oz. to 1 oz. Ed. a. Acidum Benzoicum. Ed. Grs. I to 2. Sal Benzoini. Dub. Flor res Benzoes. Lond. pneumonia. b. Tinctura Benzoes Composi-Gt. 15 to 30. Catarrh. ta. Lond. Æther Sulphuricus. Ed. Dub. Vapour inhal-Asthma. Ether Vitriolicus. Lond. ed. a. Tartris Antimonii. Ed. Gr.toreTartarum Antimoniatum. Dub. Antimonium Tar tarisatum. Lond. peated. b. Vinum Tartritis Antimonii. Dr. 1 to 2. Ed. Vinum Antimonii Tartari-Dr. † to 1. sati. Lond. c. Sulphuretum Antimonii Pre-Gr. 3-5. cipitatum. Ed. Sulphur Antimonii Precipi tatum. Lond. Sulph. Ant. Dub. to the class of expectorants, and named according to the nomenclature of the Edinburgh Pharmacopoeia, with the corresponding synonymous names of the other two colleges; in the seventh are given the usual doses of these compound medicines, and in the eighth are noted the discases to which the simple or its compound is more peculiarly adapted. The use of such tables is pretty obvious. Having Use. before him all the remedies that are suited to answer any particular indication, as in the present instance, that of promoting expectoration, the prescriber can select such articles as are best suited to the particular case in hand, or 20 Previous or which can be most easily procured; and he has at Requisites. once before him the circumstances respecting it which it is most necessary he should know. 21 Therapeutics. 22 Chemistry. 23 It is next required of a prescriber, that he be thoroughly acquainted with therapeutics, a part of the institutions or principles of medicine which instructs him in the nature and effects of the various classes of medicines as suited to different indications of cure. An extensive acquaintance with the elementary parts of chemistry is also necessary, as the subject of extemporaneous prescription forms a part of pharmacy, which is essentially a chemical art. It is therefore as impossible for a physician to be a scientific prescriber without a competent share of chemical knowledge, as for the captain of a ship to be a scientific sailor, without a knowledge of astronomy and navigation. It is certainly possible for a physician to write a prescription without having studied chemistry, and for a sailor to conduct a vessel to the West Indies without being acquainted with the mathematical principles of navigation: but these men are both empirics; they have a certain mechanical way of proceeding, which they have learned by long experience, and much more severe labour than it would have cost them to acquire a knowledge of the scientific principles of the arts which they profess. Rational It is of the utmost importance that a physician should prescription depends be able to assign a reason for every article which he inchiefly on serts in his prescriptions; that he should, as correctly as chemical possible, know what part each will act in the composiprinciples tion of the medicine, and what effect the whole compound will produce on his patient; in short, that he should not prescribe a certain formula merely because he has seen it prescribed by others in similar cases, but should form his prescription on scientific principles, and from the result of reason and reflection. In the present improved state of chemistry this is more peculiarly necessary, and it is also become much more easy. Not many years ago physicians had scarcely a clue to guide them in their prescriptions, except that of experience; they saw certain results take place, and certain effects produced, but why these results took place, or how these effects were brought about, they were almost entirely ignorant. The reasoning employed by old writers on pharmacy concerning the preparation and operation of compound medicines, is to a modern chemist highly entertaining. We shall not swell this article by specimens of such reasonings, but shall refer those who wish to amuse themselves in this way, to Strother's Lectures on the Rationale of Medicine; Quincy's Complete Dispensatory: Fuller's Pharmacopoeia Extemporanea, and the Pharmaceutical works of Dr Willis. 24 Chemical affinity. When a physician sits down to write a prescription, he should imagine the preparation going on under his eye, and should know whether or not the materials which he is ordering will act chemically on each other; and if they do, what changes will be produced. It very frequently happens that from the union of two or more substances there arises a compound possessed of very different properties, and which is likely to produce very different effects from any of the component articles. The result will sometimes be advantageous, sometimes inert, and sometimes injurious. It is the business of the prescriber to be acquainted with the advantages and disadvantages of these combinations, that he may avail himself of the former, and avoid the latter. This de 25 For want of this chemical knowledge many of the Common formula prescribed by some of our best practical writers, errors in are much less simple and scientific than they might be this point. made by an attention to chemical principles. The famous tonic remedy, commonly called Griffith's myrrh mixture, so much, and we believe, so justly extolled in cases of general debility, was originally composed in the following manner. B Myrrh dr. j. Solve terendo in mortario cum cujuslibet Spirituose dr. vi. vel unc. j. Dein adde Martis, gr. xii. Syrupi simplicis, dr. ij. m*. 26 Griffith's myrrh mixturo. * Griffith on Hectic From the gravity with which the author speaks of Fevers. this composition, and the various proportions he allows of the salt of wormwood and the salt of steel, together with the different methods of mixing the ingredients, it is pretty clear that he had no idea that any of them were superfluous or unnecessary, nor probably was he aware that the two salts act on each other, and undergo a mutual decomposition. It seems therefore to be quite an empirical prescription. Analysing it according to our present chemical knowledge, we know that the principal part of it consists of an emulsion of myrrh, containing in suspension a quantity of carbonate of iron, and having dissolved in it a small quantity of sulphate of potash, and perhaps a little subcarbonate of potash. Now, as there is no reason to believe that the two last are of any consequence in the medicine, it would surely be much more scientific to form a medicine of myrrh and carbonate of iron, with the addition of such cordials and syrups as may add to its tonic power, and render it palatable. A medicine of this kind is the following. B Pulv. Myrrh. dr. i. Carbonat. Ferri præcip. dr. 1, ལྤ• Syrup. Citri Aurant. unc. Simul tere, et adde Aquæ Menth. piper. unc. 6. Tinctur. Cinchon. compos. unc. i. M †. + Kirby's Tables, For 27 In Dr Strother's 19th lecture there is noticed a me-mal. 106. dicine which was then considered as a valuable nostrum in the cure of smallpox. The principal ingredients are, spirit of salt (muriatic acid), and salt of hartshorn (impure carbonate of ammonia). A tyro in modern chemistry need not be told that this medicine contains muriate of ammonia, produced by the combination of the acid with the alkali. If, therefore, such a medicine is useful in smallpox, it would surely be much less laborious, and much more scientific, to employ the muriate of ammonia, commonly called sal ammoniac, which we have prepared to our hands. As the secondary salts form a class of bodies which constitutes a considerable part of the materia medica, it is proper for the physician to be intimately acquainted with their nature and chemical properties. Here he will again find the advantage of systematic tables, con taining 28 Previous taining the principal circumstances respecting the com- view, only divided, for the sake of convenience, into Previe 29 lana Insoluble. In this first part of the table of secondary salts there are five columns, in the first of which are set down the names of most of the secondary salts employed in medicine, according to the most approved chemical nomenclature. The second column shews the degree of attrac tion which subsists between each salt and water, namely, how many parts of water at the temperatures of 60° and 212° of Fahrenheit are required to dissolve one part of the salt, in the state in which it is usually employed, DECOMPOSITION BY SINGLE AFFINITY. Barytes. Soda. Lime. Magnesia. Ammonia. Tannin. Gallic Acid. Oxalic Acid. VOL. XVII. Part I. and whether the salt be deliquescent or efflorescent. Previous Requisites. |