prises the chief portion of the daily work of the pharmacist, and can only be learned at the dispensing-counter and under the personal supervision of a competent master. In the following pages are given the most important of the general directions pertaining to this subject, with the object of enabling the young medical practitioner to familiarize himself with the compounding and dispensing of drugs so far as the limits of the book will admit of. The drug-store of the present day has degenerated so far from its legitimate business that ere long physicians will be compelled in self-defence to dispense their own medicines, thereby protecting themselves and their patients from the patent-medicine vending, the counter-prescribing, and the many other nefarious methods which have degraded the pharmacist from his old professional position to that of a mere trader in drugs and nostrums. The first outfit of every young doctor should include a few pharmaceutical instruments and a small stock of drugs. By daily handling of these, the tools of his profession, he will insensibly become familiar with the technique of the art, and even if he does not continue to dispense his medicines in after years he will never regret the practical knowledge which such a course will give him. Compounding means the mixing or preparing of the drugs ordered in a prescription, and comprises all the operations of official pharmacy together with many other manipulations which will be described in their appropriate places. Dispensing is the operation of putting up and issuing the drugs ordered in a prescription, and may apply to the already compounded preparations of official pharmacy as well as to those prepared extemporaneously. WEIGHTS AND MEASURES. The working formulæ of the U. S. Pharmacopoeia are constructed on the system of parts by weight for all articles whether fluids or solids, except in the case of fluid extracts, for which the metric weights and measures are employed. On this system it really makes no difference what unit of weight is adopted in official pharmacy. However, the weights and measures referred to by physicians in prescribing and used by pharmacists in dispensing medicines are in the United States those of the Apothecaries' or Troy System of Weights (having 480 grains to the ounce and 5760 grains to the pound) and the Wine Measure, or those of the Metric System. On the other hand, the British Pharmacopoeia recognizes only the Imperial Standard (Avoirdupois) weights, having 43772 grains to the ounce and 7000 grains to the pound. The drachm (60 grains) and the scruple (20 grains) are intermediate units which are still used but are rapidly becoming obsolete. The units of the Wine Measure are the minim (m), which in water at its maximum density equals gr. 0.95; the fluidrachm (60 minims) and the fluidounce (8 fluidrachms or 480 minims). The signs used to denote these units are m minim, scruple, 3 drachm, 3 ounce, and in the cases of liquids an f to denote fluid is often placed before the sign, thus f3 for fluidrachm, f3 for fluidounce. The relations between these units of weight and measure are as follows: Measure. Weight, I Weight. Measure. mj, One minim = 0.95 grains. grain j= 1.05 minims. 13 j, One fluidrachm = 56.96 " 3j= 63.20 “ f3j, One fluidounce = 455.69 " 3j = 505.60 " The Troy ounce contains 4212 grains more than the avoirdupois ounce, but the Troy pound contains 1240 grains less than the avoirdupois pound. The grain is the only unit common to both. Table of Apothecaries' or Wine Measure. Minim. Fluiduncia. Fluidrachma. Minimum. m 8 1024 61440 T = 16 7680 0. 128 4.80 60 Table of British Imperial or Pharmacopæial Measure. Fluidounce. Fluidrachm. Minim. Fluiduncia. Fluidrachma. Minimum. min. 76800 20 = 9600 8 60 160 = 480 The Metric, or Decimal System of Weights and Measures, is generally used on the continent of Europe, and also by French and German physicians in the United States. Its three standard units are the following, viz.— • A Meter, the standard unit of linear measure and also of the whole system, is the ten-millionth part of the quadrant of the earth, i.e., the forty-millionth part of the earth's circumference around the poles. One-tenth of the meter is the Decimeter, one-hundredth is the Centimeter, and one-thousandth is the Millimeter. A Liter, the unit of measures of capacity, is the cube of a decimeter. One. thousandth of a liter is the Cubic Centimeter, which measure of pure water at its maximum density weighs one Gramme. A Gromme, the unit of weight, is the weight of the one thousandth part of a liter of water at its maximum density. Its tenth is the Decigramme, its hun. dredth is the Centigramme, and its thousandth part is the Milligramme. The metric measures above noted are those used chiefly in pharmaceutical practice, but the system embraces many other terms of increase which are set forth in the following table. 10000 Myriameter. 10000 Myrialiter. 10000 Myriagramme. 1000 Kilometer. 1000 Kiloliter. Kilogramme. 100 Hectometer. 100 Hectoliter. Hectogramme. 10 Dekameter. Dekaliter. 10 Dekagramme. Meter. Liter. Gramme. .I Decimeter, 1 Deciliter. .1 Decigramme. .o1 Centimeter. .01 Centiliter. o1 Centigramme. 001 Millimeter. .001 Cubic Centimeter 001 Milligramme. or Milliliter. The relations between the Metric Weights and Measures and the Apothecaries' are as follows, viz. I meter = 39.370432 inches. I minim = 0.0161613 cubic centimeter. The Metric System is making way but slowly in this country although its progress is aided by every process of forcing 1000 which scientific bodies can bring into action, and it remains to be seen how much its adoption in the last edition of the U. S. Pharmacopoeia will influence the medical profession in its favor. With all the influence brought to bear in its favor it certainly has not yet been adopted by any considerable proportion of native-born and home-educated physicians and pharmaceutists. Its chief disadvantage is one which is inherent to any decimal system, viz.-that the number ten cannot be divided more than once without producing a fraction. This is partly compensated for by the practice of dividing five into the three parts of 2, 2 and 1, and on this principle metric weights are usually constructed. In writing or reading prescriptions it is sufficiently accurate to consider a gramme as equivalent to 15 Troy grains, and a cubic centimeter (milliliter) as equivalent to 15 minims, or one-fourth of a fluidrachm. All other terms, units or prefixes belonging to the metric system may be wholly ignored by the physician and the pharmacist. The decimal point after the gramme or the cubic centimeter should always be replaced by a line so as to avoid errors which in many cases might prove serious from the misplacement of a point, the dropping of a spot of ink or the intrusion of a fly-speck. The simplest method of writing a metric prescription for one not practiced in the system is to first write for one dose of the medicine in grains and minims, then by substituting the same number of grammes and cubic centimeters (fluidgrammes) we get fifteen doses in metric terms. Of course when a mixture or solution is desired the proper quantity of vehicle must be added to give the dosage in such measures as may be deemed convenient for administration. For example, One dose. 15 doses metric. 016 Syrupi, . . . . . mix, This gives a two-ounce mixture approximately, of which the dose would be "a teaspoonful thrice daily.” One dose. R. Quininæ Sulphatis, . . . gr. ), Massæ Ferri Carb., . . . gr. i), Ext. Nucis Vomicæ, . . gr. 4 or 0.25, 60 15 doses metric. The above rule will answer for all liquids except those which are very heavy (as Syrups and Chloroform), or very light (as Ether). Measures may be entirely discarded, and all fluid quan tities expressed in grammes. The average drop of water may be considered equivalent to 0.05 cubic centimeter (or gramme), the average teaspoonful to 5 c.c., the tablespoonful to 20 c.C., the Troy 3 to 30 grammes, the fluidounce to 30 C.C., and 8 fuidounces to 250 C.C. In prescribing Syrups or Chloroform, each Troy fluidounce should be reckoned at something more than 30 grammes--say 40; and if this be done, the difficulty of converting one scale into the other will be obviated. As to Syrups, Chloroform, etc., the following table shows the actual weight in grammes of each fluidounce of the substances named : Water. Tinctures. Syrup. Chloroform. Ether (Grammes.) (Grammes.) (Grammes.) (Grammes.) (Grammes.) 29.52 28,00 38.00 43.70 22.14 118.08 112.00 152.00 174.80 88.56 A table of equivalents between Apothecaries' and Metric Weights and Measures will be found in the Appendix. Approximate or Domestic Measures become necessary in apportioning doses for a patient, when liquid medicines are used. Of these the measure most commonly employed is the teaspoonful, which is generally taken as equivalent to a fluidrachm, though in most cases as now manufactured the teaspoon contains about 75 minims, or 25 per cent. more than the theoretical quantity. The dessertspoonful is about equal to 2 teaspoonfuls, and the tablespoonful to about four teaspoonfuls or fzss, while the wineglass is supposed to contain about f3ij. The use of graduated medicine-glasses is strongly recommended instead of the above approximate measures. They may be obtained at a trifling cost in any well-stocked drug-store. Drops (Gutta) are very variable in size, though popularly supposed to equal minims, the variations in their relative dimensions being due to the viscidity of the liquid, the shape and surface of the orifice from which they escape, and sundry other circumstances. The Syrups and Mucilages produce large drops, while Bromine, Chloroform, and other heavy mobile liquids produce very small ones. These differences are well illustrated in the following table which gives the number of drops in a Auidrachm of several liquids of certain classes. |