The weights employed in prescription writing are the milligram, centigram, decigram, gram, and kilogram. The other terms in the following table are but rarely employed abroad and never among English-speaking physicians. It will be seen that one Kilogram represents 1000 Grams.

10 milligrams

make

1 centigram.

10 centigrams

"

1 decigram.

10 decigrams

"

1 Gram.

10 Grams

"

1 Dekagram.

10 Dekagrams

"

1 Hectogram.

10 Hectograms

"

1 Kilogram.

10 Kilograms

"

1 Myriagram.

Abbreviations for the different divisions and multiples of the Gram, with their corresponding equivalents in grains, are as follows:

1 milligram is written

1 mg.,

or Gm.

.001,

equal in grains to (1/64)

.015432

1 centigram "

1 cg.,

" Gm.

.01

" ' ' (1/6)

.15432

1 decigram "

1 dg.,

" Gm.

.1,

" "

1.5432

1 Gram "

1 Gm.,

" Gm.

1.,

" "

15.432

In writing prescriptions a physician uses but one system, the metric or the apothecaries'; therefore to write prescriptions properly he does not need to know how to convert from one system to the other. He learns one system and adheres to that.

But to read and understand prescriptions written or spoken in the system other than the one he employs, he must translate them into his own system, and this requires a knowledge of equivalents. Knowing the approximate equivalents, it is then merely a matter of multiplication or division to convert a prescription of one system into a prescription of the other system.

Examples of conversion are:

1 milligram = 1/65 grain: 5 milligrams = 5/65 = 1/13 grain

1 grain= 0.065 Gm., therefore, 2 grains = 2 X 0.065 Gm.

= 0.13 Gm., and 1/100 grain = 1/100 X 0.065 Gm.

= 0.00065 Gm., etc. 1 ounce= 30.0 Gm.: 4 ounces = 30.0 X 4 = 120.0 Gm.