This section is from the book "Text-Book Of Materia Medica For Nurses", by Lavinia L. Dock. Also available from Amazon: Text-book of materia medica for nurses.

This system of weights and measures, first instituted by the French, is now in general use on the Continent of Europe, and is legalized in the United States, where it is employed in certain departments of the government and by scientific people at large. Most physicians and surgeons make use of the system, particularly in the prescription of medicines and in operating-room work. It therefore has become necessary that a nurse should understand it, while its simplicity, convenience, and accuracy commend the system to everyone.

The metric tables which most concern a nurse's work are as follows:

1 milligramme (mg.) = | 0.001 gramme. |

1 centigramme (cg.) = | 0.01 " |

1 decigramme (dg.) = | 0.1 " |

1 gramme (Gm.) = | 1.0 " |

1 decagramme = | 10.0 grammes. |

1 hectogramme = | 100.0 " |

1 kilogramme = | 1000.0 " |

1 millimeter (mm.) = | 0.001 meter. |

1 centimeter (cm.) = | 0.01 " |

1 decimeter (dm.) = | 0.1 " |

1 meter (m.) = | 1.0 " |

In describing dosage and quantities of fluid the term cubic centimeter has been discarded by the U. S. P. as the cubic centimeter is not an exact thousandth of the milliliter. The term now used instead of Cc. is "mil," the first syllable of milliliter.

1 milliliter or mil (ml.) | =0.001 liter. |

1 centiliter (cl.) = | 0.01 |

deciliter (dl.) = | 0.1 |

I liter (1.) = | 1.0 |

In writing dosage or strengths according to the metric system, the numerals are written in Arabic characters and are followed by the proper abbreviation, as, 2 mils, 1 Gm. The abbreviation for gramme has always a capital to distinguish it from gr. But in writing by the apothecaries' system Roman numerals are employed after the symbol or abbreviation, as 3 i., gr. i.

The primary unit of the metric system is the meter, (39.37 inches), which is approximately one ten-millionth part of the distance from the equator to the north pole; and from this as a basis the units of weight and capacity are readily derived, the remaining measurements in each table being obtained from their units by decimal subdivision and multiplication. It will be observed that any term less than the unit is expressed by the aid of a Latin prefix (deci, centi, milli), while Greek prefixes (deka, hecto, kilo) express multiplication, or terms greater.

To mention the correspondence between the metric denominations and those of the United States currency, which is a metric currency, may serve to make understanding more clear. It will be noticed that meters- for instance - correspond to dollars, decimeters to dimes, centimeters to cents, and millimeters to mills. Somewhat analogous to our method of reading currency is that of reading the metric system generally.

For instance in the figures $5.25 we have represented dollars and cents, the latter being equal to 25/100 of a dollar. Similarly in the metric system these figures would stand for 5 and 25/100 of whatever the measure might be - whether of length or of capacity.

Practically, of the table of capacities the liter and its multiplications only are used, as the mil is more convenient for small quantities. Formerly, instead of the liter, the term 1000 Cc. was employed. The cubic centimeter (Cc.), centimeter (Cm.), and gramme (Gm.) are the terms the nurse most often meets with. The method of obtaining the gramme, the unit of the standard for weighing both solids and liquids, has been explained.

20 grains = I scruple = 60 grains = I drachm = ʒ 8 drachms as I ounce = ℥ = 480 gr. 12 ounces = I pound = lb. = 5760 gr.

60 minims = 1 fluid drachm = ʒ 8 fluid drachms = 1 fluid ounce = ℥

16 fluid ounces = 1 pint = O. 8 pints = 1 gallon = gal.

1 grain = 0.065 Gm.

1 ounce Troy = 31.103 " I pound avoirdupois = 453.600 "

1 fluid drachm = 4 mils.

I fluid ounce = 30 "

1 pint = 480 "

1 inch = 2.539 Cm.

I gramme = 15.432 grains.

1 kilo = 2.204 lbs. avoirdupois.

I cubic centimetre = 16.23 minims.

1 liter = 33.81 fluid ounces.

1 centimeter = 0.393 inch.

1 meter = 39.37 inches.

1 mil = | 15 minims. |

4 mils = | 1 fluid drachm. |

30 mils = | 1 " ounce. |

1 gramme = | 15 1/2 grains. |

1 decigramme = | 1 1/2 grains. |

1 centigramme = | 1/6 grain. |

1 milligramme = | 1/64 grain. |

1 liter = | 1 quart. |

1 kilo = | 2 1/5 lbs. avoirdupois. |

1 cm. = | 2/5 inch. |

To obtain the number of grammes, approximately, reduce the quantity to grains and divide by 15. Or

Reduce the quantity to drachms and multiply by 4; and proceed on like principles with other denominations.

It may be interesting to note how often 15 or some multiple of 15 comes into use in measuring medicine by the metric system or in the ordinary way. Thus, 1 grain is equal to about 60 milligrammes; 15 grains are equal to about 1 gramme; 60 minims are equal to 1 drachm, or a teaspoonful, or about 4 grammes; 30 grammes are equal to about 1 ounce; and 15 milligrammes are equal to about 1 tablespoonful. For one who is accustomed to the use of the ordinary measures only three of these equivalents will be necessary in order quickly and easily to transfer doses from one system to the other. These are:

1 gr. = 60 milligrammes, approximately 15 gr. = 1 gramme "

1 3 = 30 grammes "

The following approximate equivalents may be used:

4 mils = 1 fluidrachm = 1 teaspoonful = 60 minims.

8 mils = 2 fluidrachms = 1 dessertspoonful = 120 minims.

15 mils = 4 fluidrachms = 1 tablespoonful = 240 minims (U. S. P., ix., p. li ).

Table showing quantities from five grains down, according to the old tables, with their equivalents under the metric system:

Grains | ||

Grammes. | in decimal fractions. | in common fractions (approximate). |

0.324 | 5 | 5 |

0.29I | 4.5 | 4 1/2 |

0.259 | 4 | 4 |

0.226 | 3.5 | 3 1/2 |

0.194 | 3 | 3 |

0.162 | 2.5 | 2 1/2 |

0I30 | 2 | 2 |

0.097 | 1.5 | 1 1/2 |

0.065 | 1 | 1 |

0.061 | 0.94 | 15/16 |

0.060 | 0.93 | 9/10 |

0.057 | 0.88 | 7/8 |

0.053 | 0.82 | 18/16 |

0.050 | 0.77 | 3/5 |

0.049 | 0.76 | 5/8 |

0.045 | 0.69 | 11/16 |

0.040 | 0.62 | 10/16 |

0.036 | 0.56 | 9/16 |

0.032 | 0.5 | 1 |

0.O28 | 0.43 | 7/16 |

0.025 | o.39 | 3/5 |

0.024 | o.37 | 3/5 |

0.020 | 0.31 | 5/16 |

0.0l6 | 0.24 | 1/4 |

0.0I2 | 0.18 | 3/16 |

0.008 | 0.12 | 1/8 |

0.004 | 0.06 | 1/16 |

0.0032 | 0.05 | 1/20 |

0.0027 | 0.04 | 1/25 |

0.0022 | 0.033 | 1/20 |

0.00I8 | 0.028 | 1/36 |

0.00l6 | 0.025 | 1/40 |

0.00I3 | 0.02 | 1/50 |

0.00II | 0.017 | 1/60 |

0.00I | 0.015 | 1/64 |

0.0006 | 0.01 | 1/100 |

0.0005 | 0.008 | 1/128 |

0.0004 | 0.0065 | 1/160 |

0.0003 | 0.005 | 1/200 |

0.0002 | 0.003 | 1/320 |

0.000I | 0.0015 | 1/640 |

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