This section is from the book "A Manual of Materia Medica and Pharmacology", by David M. R. Culbreth. Also available from Amazon: Manual of Materia Medica and Pharmacology.

Prescriptions (L. praescriptio, a writing before, an order; fr. prae-scrib(o)-ere, to write before, to ordain) are ex tempore formulae written in Latin, usually at the bedside, to combat specific conditions, and in their construction certain rules, forms, and requisites must be observed:

**Chirography**. Learn to write legibly, letting your style be plain, neat, thoroughly intelligent without possible ambiguity or doubt for the compounder as to what is intended. Make this your first imperative duty, and if, when a student, your penmanship is indifferent, then at once begin the trial for improvement; this can and will alone come by careful practice, so make sure that you know how to write before knowing what to write.

**Prescription Blanks**. Do not be careless as to the kind and style of paper used, It is well to have uniformity in blanks, and whenever your regular supply becomes exhausted, if possible, replenish at once, using in the interim good, white, unruled paper cut to a specific size. A neglect of this might occasion discourteous remarks somewhere along the line (by attendant, compounder, etc.), which should and can easily be avoided. Blanks are, as a rule, furnished gratuitously by the druggists (who are only too well pleased to have the number great), and in size should be neither too large nor too small, but in keeping with the boldness of individual handwriting. On the other hand, when the style and printing of those supplied are not satisfactory, then others more to one's liking should be secured from the printer at your own expense.

**Weights And Measures**. Of these we may employ three systems: 1. Avoirdupois (Imperial). This has the following subdivisions: grain (gr.), drachm (drm.), ounce (oz.), pound (lb.), and is thus proportioned: 27.35 grains make 1 drachm, 16 drachms make 1 ounce (437} grs.), 16 ounces make 1 pound (7,000 grs.), 27.35 - 437} - 7,000. By this system all substances are sold except precious stones, prescription-whitish.

precious metals, and drugs when prescribed by a physician directly or indirectly for sickness.

2. Apothecaries' (Troy). This has the following subdivision-: grain (gr.), scruple (Э), drachm (3), ounce (3), pound (lb.), and is thus proportioned: 20 grains make 1 scruple, 3 scruples make 1 drachm, 8 drachms make 1 ounce, 12 ounces make 1 pound, 20 - 60 - 480 - 5,760. The difference between the two pounds mentioned is 1,240 grains, the two ounces 42 grains, the two drachms 32.65 grains. The grain, however, is the same the world over, and is the unit of weight.

United States Fluid, Liquid, or Wine Measure. This has the following subdivisions: minim (e), fluidrachm (f3), fluidounce (f℥), pint (O), gallon (Cong.), and is thus proportioned: 60 minims make 1 fluidrachm, 8 fluidrachms make 1 fluidounce, 16 fluidounces make 1 pint (2 pints make 1 quart), 8 pints (4 quarts) make 1 gallon, 60 - 480 - 7,680 - 61,440 (58,340 gre.). The minim is the unit of capacity, and weighs 0.95 of a grain, the ounce weighing 455.7 grains.

Imperial Liquid Measure (Gt. Britain). This has the following subdivisions: minim (min.), drachm (fl. dr.), ounce (fl. oz.), pint (O), gallon (C). and is thus proportioned: 60 minims make 1 drachm, 8 drachms make 1 ounce, 20 ounces make 1 pint, 8 pints make 1 gallon, 60 - 480 - 9,600 - 76,800 (70,000 grs., or 10 lbs. Avd.). This minim weighs 0.91 of a grain, the ounce weighs 437.5 grains. It is thus seen that we have two minims (0.95 - 0.91 grain) and three ounces (437.5 - 455.7 - 480 grains).

3. Metric, Decimal, or French. This system is based upon the earth's polar circumference (24,818 miles), of which the one-forty-millionth part, 39.37 inches, is taken as the unit of length (metre); of the metre one-tenth, 3.93 inches, is taken, and upon it a cube constructed, which contains of distilled water 1,000 Ml. (Cc.) or Gm., and this furnishes the unit of capacity (litre); again, of the metre the one-hundredth part, .393 of an inch, is taken, and upon it a cube constructed, which contains of distilled water 1 Ml. (Cc), weighing 15.434 grains, and this furnishes the unit of weight (gramme).

Milli-metre, | mm., | -litre, | ml., | -gramme, | mg. | = | .001 |

(Cubic centimetre, Cc,) | |||||||

Centi-metre, | cm., | -litre, | cl., | -gramme, | cg. | = | .01 |

Deci-metre, | dm., | -litre, | dl.. | -gramme, | dg. | = | .1 |

Metre, | M., | Litre, | L, | Gramme, | Gm. | = | 1. |

Deka-raetre, | Dm., | -litre, | Dl., | -gramme, | Dg. | = | 10. |

Hectometre, | Hm, | -litre, | HI., | -gramme, | Hg. | = | 100. |

Kilo-metre, | Km., | -litre, | Kl., | -gramme, | Kg. | = | 1,000. |

Myria-metre, | Mm., | -litre, | Ml., | -gramme, | Mg. | = | 10,000. |

Here every unit is multiplied or divided by 10, consequently each preceding denomination is just 10 times smaller than the one that follows, thus it takes 10 millimetres to make 1 centimetre, 10 centimetres to make 1 decimetre, etc.

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