Metrology is the science of measure. The term was originally used to express the measure of distance, but now is understood to include measures of quantity also.

Weight is the sum of the attraction of gravity existing between the earth and a body on its surface.

The origin of standards for weights and measures is an interesting study. Josephus states that Cain after leaving the neighborhood of Eden introduced among his new neighbors means for weighing and measuring. It might be believed that these were also the first crooked weights and measures.

The origin of some of the familiar units seems decidedly crude. The grain from a grain of wheat; the foot from the length of the pedal extremity; the cubit, the distance from the elbow to the tip of the fingers; the hand, the distance from the tip of the abducted thumb to the edge of the ulna side of the hand; the span, the distance between the tips of the little finger and the thumb when separated as widely as possible.

There are now in use in the United States several standards with which the physician and pharmacist must be familiar. It should be one of the duties of every member of both professions to lend his influence toward the much desired end, that the metric system alone be used by the entire world.

Table of Avoirdupois Weights.

This table is never used in prescribing.

These are the weights that are used almost exclusively in buying and selling all solid and many liquid drugs. A physician who orders a "pound"gets an Avoirdupois pound, or 7000 grains.

If he orders an"oz."he receives an Avoirdupois ounce of 437.5 grains, as"oz."stands for the Avoirdupois ounce only. Potent drugs, as strychnine, morphine, etc., are usually handled in 1/8-oz. bottles. It should be remembered that these do not contain 1/8 of an Apothecaries' ounce, or 60 grains, but 1/8, of an Avoirdupois ounce, or about 54.7 grains.

Table of Apothecaries' (or Troy) Weights.

It should be remembered that the grain here is the same as the Avoirdupois grain.

The ounce contains 480 grains as against 437.5 of the Avoirdupois.

The pound contains 12 ounces of 480 grains, or 5760 grains instead of the Avoirdupois pound of 16 oz. of 437.5 grains each, or 7000 grains.

Of this table only the grains, drachms, and ounces should be used in prescription writing. The scruple is still sometimes employed, but its use should be discouraged, as it is altogether unnecessary, and the character when carelessly made or blurred is too easily mistaken for the character for the drachm.

Table of Apothecaries' (or Wine) Measure.

Some points to remember are:

The character 5 represents 60 grains, while f3 represents 60 minims. represents 480 grains only, while is necessary to express 480 minims.

A minim is not the equivalent of a grain. 480 minims (1 ) of water weighed at the standard temperature weighs 456.37 grains. This should be remembered for percentage solutions.

Specific gravities of liquids vary; a pint of a liquid is not necessarily a pound.

Two pints make 1 quart and 4 quarts make 1 gallon, but the employment of the quart is hardly considered good form in medicine and pharmacy.

In prescriptions where Apothecaries' weights and measures are employed, quantities are expressed in Roman numerals. In printed matter the small letters are used, while in writing it is necessary to sacrifice grammatical exactness on the altar of caution to the extent of using a capital L as the small letter might be too easily mistaken for an i. It is customary to make the letters harmonize in size, as:

It is also customary to draw a line over the letter or group of letters expressing the quantity, and the greatest care should be used in printing them. The numerals i and j should be dotted, but under no circumstances should the others be dotted, as in a hastily written or blurred prescription the pharmacist often depends on the dots to differentiate an indistinct i from an l or a comma or period, or a j from an imperfectly formed v, as in the following:

They should also not be written together as:

Final i is made j as an additional safeguard (see above). When poorly written or when an imperfect effort is made to follow the numerals with a comma or period, there is more danger of confusing an i than a j with a punctuation mark. The j means the last numeral in that quantity, and any mark following it is understood to be an accident, artefact or punctuation. .

Table of Approximate Measures.

It should be remembered that these equivalents are far from correct. It is not unusual to see teaspoonfuls measured that really amount to anywhere from 30 to 120 minims. It is always the better policy to have a family use a graduated glass, which will either be supplied free by the pharmacist as an advertisement or can be purchased at a nominal price.

When regular spoons, glasses, etc., are used, the physician on his first visit should select the ones that are best suited and have them set aside for the particular use.

The so-called"glassful"varies from 6 to 14 ounces. There may be much difference between a tablespoonful of brandy and one of codliver oil, or a glassful of purgative water and one of beer. With the expenditure of a small amount of effort any prescriber can so familiarize himself with spoons and glasses as to readily estimate their capacity.