AN ANSWER 
TO 
“A PROTEST AGAINST THE USE OF THE 
METRIC SYSTEM IN PRESCRIBING.” 
BY 
D. WEBSTER PRENTISS, M.D., 
WASHI NGTON, D C. 
FROM 
THE MEDICAL NEWS. 
November 24. 1883. AN ANSWER TO 
“A PROTEST AGAINST THE USE OE THE 
METRIC SYSTEM IN PRESCRIBING.” 
Sir: In your issue of November 3d inst. appears a 
letter from Dr. James Orr, of Texas, under the above 
heading. I do not desire to provoke a controversy, 
but, as an advocate of the “ metric system,” I cannot let 
this statement go unanswered. 
Your correspondent is peculiarly unfortunate in the 
three points which he submits as arguments against the 
new system, for in each one of them he is in error, and 
in each one of them is the converse of his conclusion 
true. He says: ” 1. In calculating the given quantity 
of a drug desired in a prescription, it can be done 
quicker by our or the English weights—grs., 3, 5, etc.” 
This is true certainly of a physician who knows doses 
only in the old system. But if he knows the doses in 
the metric system equally as well as in the old—which 
is the proper standard of comparison—the metric sys- 
tem is infinitely the easier and quicker method of cal- 
culating quantities. Let us take an example. The 
dose of morphia is one centigram (0.01); the dose of 
chloral hydrate is one gram (1.00). We wish to write 
a prescription which shall contain six doses, of a table- 
spoonful each. Six tablespoonfuls make one hundred 
grams. We have 
i 
Old 
Grams. 
Decimals. 
System. 
U.—Morphia; Sulph. . . o 
06 
'gr. i. 
Hydrat. Chloral. . . 6 
3ivss. 
Syr. Aur. Cort. . . 25 
qiv. 
Aquae, . . . ad 100 
3«j. 4 
What can be simpler than this? There is but one 
unit, the gram and its decimal parts, written in plain 
Arabic numerals. It is equally easy to write the same 
or any other prescription for any number of doses, the 
only thing requisite being a knowledge of the dose in 
metric terms. Of the difficulty encountered when one 
does not know the dose in metric terms, but must 
laboriously translate it from the incongruous weights 
and measures of the old system, I have nothing to say. 
The same R. in the old system is given alongside 
the metric R. Who that is unprejudiced can say that 
it is simpler ? There are four different units—grains, 
scruples, drachms, and ounces—related to each other 
by different and arbitrary ratios. 
Three of them, scruples O), drachms (3), and ounces 
(.5), are represented by arbitrary and unmeaning hiero- 
glyphics, and the quantities are expressed in the awk- 
ward Roman numerals, instead of the Arabic numerals 
in common use. Another point which illustrates the 
superiority of the metric over apothecaries’ weights 
in calculating quantities, is the use of percentages. 
In making lotions, collyria, etc., we speak of so much 
per cent, strength ; as a five per cent, solution of car- 
bolic acid for a dressing to a wound. 
What is simpler than writing 
R.—Acidi carbolici, ... 5 grams. 
Aquae, .... 100 “ —M. 
Use as lotion. 
Calculate a five per cent, solution in grains and 
ounces, and see how great is the difference in simplicity 
and trouble. With just as great ease can any per- 
centage be written for. 
2. The second point of Dr. Orr is, that there is greater 5 
liability to error in the metric prescription than in the 
old form. If he compares a physician familiar with 
the old system, writing in the old way, with one who 
is also familiar with the old, but does not know the 
new—writing in the metric terms—he is probably right. 
But such a comparison is unfair. If we compare phy- 
sicians equally familiar with the system in which they 
write, the advantage is altogether in favor of the metric. 
In the latter there is but one unit; the quantities are 
written in ptain figures and the aggregate shows the 
proportionate quantity of each. In the former there are 
as many units as are found in the tables of apothecaries’ 
weights and measures ; they are expressed by arbitrary 
hieroglyphics; quantities are in Roman numerals, and 
the aggregate does not show the proportion. 
How often does it happen that a physician looking 
over a prescription he has written, finds he has written 
the drachm mark where he meant scruple, or vice versa. 
How is the pharmacist to know which is meant ? To 
be sure it is careless writing, but it occurs continually, 
as the pharmacist’s R files will testifiy. Such a blunder 
cannot be made in the new system.. As to the danger 
of misplacing the decimal, this is obviated by the use 
of the decimal line ; then if a mistake is made, we have 
no apology to offer. It is just as reasonable to expect 
the merchant in his ledger, to charge his customer ten 
cents a yard for silk, instead of ten dollars, by putting 
it in the wrong column. 
In fact, the decimal system applied to medicine is 
identical with our cental currency applied to money. 
It needs no argument to prove that our present money 
system is preferable to the old-fashioned “ ftps” [6% 
cents), “levies” (121/2 cents), “ picayunes,” and “York 
shillings,” or that it is far superior to the English sys- 
tem of £, shillings, pence, and farthings. Yet exactly 
the same differences hold in medicine between the new, 6 
or metric system, and the old, or apothecaries’ weights 
and measures. I think, however, no one among us, 
not even the “ oldest inhabitant,” would be willing to 
exchange our dollars, dimes, and cents for the British 
coinage, or even return to the good old times of Col- 
onial coinage. 
The third point of I)r. Orr is that “ It takes less time 
and space to write the old method.” The only answer 
we need make to this statement is, that the difference 
in point of space between the old and the new is that 
in the former the value of each quantity, as gr. 
or 3, must be written with the amount, whereas, in the 
latter, there is but one unit, and only the quantities are 
given. This would make it appear that the “old 
method ’’takes more space than the new. 
In the specimen of prescription given, a very poorly 
written metric prescription is chosen. I repeat it here 
in order to show how such a prescription should have 
been written, and then leave it to the impartial reader 
to judge whether it is so complicated or difficult to 
understand. The prescription Dr. Orr gives is as fol- 
lows : 
“H.—Morph. Muriat., . . . .0060. 
Tinct. Cannab. Ind 0800. 
Chloroform i, . . . .1350. 
Ol. Menth. Pip., . . . .0025. 
Tinct. Capsici, 0025. 
Acid. Hydrocyanici Dil 0170. 
Alcohol, 3000. 
Glycerinae, 4570.—M.” 
No dose is stated, but from the amounts I should sup- 
pose this to be intended for one dose. I cannot imagine 
who could have written such a prescription, and 1 do 
not wonder at any physician finding fault with it. It 
certainly violates every rule of correct prescribing, and 7 
must, I think, have been (in the journal from which 
copied) a clumsy attempt to translate grains and parts 
of grains into metric terms. 
The observance of a few simple rules are a wonder- 
ful help to correct and easy prescribing : 
1. The ingredients should be placed in the order of 
their strength and importance. If the mixture contains 
both solids and liquids, place the solids first in this 
order, and then the liquids, in like order. 
2. Write down first all the ingredients intended to 
be ordered. 
3. Determine the number of doses to be given in the 
prescription, and make the quantities to correspond. 
4. If a liquid is ordered, let the vehicle be named 
last, and by placing after it the term “ ad,” or “ad q.s.” 
let it show how much the entire prescription calls for. 
In this way there is no necessity of adding up the 
amounts to see how much they make. 
Now for this objectionable R—under these rules. 
We write down the ingredients in proper order, and 
determine to make twelve doses, of a dessertspoonful 
each. 
This R is supposed to be an anodyne, for internal 
administration. The doses in the above copy of some 
of the ingredients are decidedly homoeopathic. We 
shall give the usual doses, as follows : 
R.—Morphiae Sulph. (dose, 0.01), . .012 
Ol. Menth. Pip. (dose, 0.05), . . 060 
Ac. Hydrocyan. Dil. (dose, 0.10), . 1 20 
Chloroformi (dose, 0.30), . . . 360 
Tr. Cannab. Ind. (dose, 2.00), . . 24 
Tr. Capsici (dose, 2.00), . . .24 
Glycerinae (dose, 2.00), . . .24 
Alcohol ad, 10000 
M. S. Dessertspoonful every 4 hours in water, until 
relieved. 8 
It is not very often, I believe, that a physician writes 
as complex a prescription as this one, but when he 
does, he needs the metric system. A comparison be- 
tween this and the example given in the paper criti- 
cised, will show the difference between a properly and 
an improperly written metric prescription. 
K 
METRIC PRESCRIPTION. 
Grams. 
Decimnl. 
<U 
t 
4> 
> 
o 
Metric System in Medicine. 
Old Style. Grams. Decimal. 
i grain or i minim equals 
.. 0 06 
15 grains or 15 minims equal 
.. I OO 
rT 
1 dram or 1 fluidram equals 
... 4 00 
<L) 
V 
1 ounce or 1 tluidounce equals.... 
..32I00 
The Cubic Centimeter (C. C.) may be consul- 
Ct 
ered identical with the gram for water or aqueous 
solutions. 
Liquids lighter or heavier than 
water should 
either be weighed or a proper allowance be made. 
Being a pioneer in the metric line in my own city 
some four years ago, I anticipated trouble from the 
pharmacists in connection with my prescriptions. But 
few of them were familiar with the system, and at first 
there was some grumbling; but when they learned 
how simple it is, and obtained the weights and meas- 9 
ures, there was no more trouble. Now I do not believe 
there is a pharmacist in the District of Columbia but 
prides himself on being able to compound “ metric 
prescriptions.” I enclose the form of prescription 
blank which 1 have always used. The reverse con- 
tains brief but ample directions for converting the 
metric terms into apothecaries’ weights, for the benefit 
of such druggists who may not have metric weights. 
This letter is in a measure an advocacy of the metric 
system, but space does not allow of any extended argu- 
ment to prove its superiority. I will, therefore, close by 
stating briefly some of the reasons for its adoption 
generally : 
1. Its simplicity— 
One unit of length i = the meter. 
One unit of capacity = the liter. 
One unit of weight — the gram. 
One unit of cubic measure == the ster. 
One unit of sq. measure = the are. 
The divisions and multiples of these units are by tens. 
At present there are over seventy arbitrary units in use 
in the United States. 
2. Its substitution for our present system of weights 
and measures would save an immense amount of time 
and labor in all forms of business. It would save one 
year of school life for every child. In Appleton’s 
Cyclopcedia, under article weights and measures of the 
United States, over seventy units are given as in use, 
and they are utterly independent of any systematic 
relation to each other. Think of having to multiply by 
1728 to find how many cubic inches are in 1883 cubic 
feet! Yet this is but one item of but one of the miser- 
able tables that all our school children are obliged to 
memorize. And not that only, but these heterogeneous 10 
tables must be applied to all the examples in arithmetic 
to be worked out during all the years the unfortunate 
juvenile is at school. 
3. The metric system is the cosmopolitan system. 
It is legalized by twenty-three nations of the civilized 
world, and is in exclusive use in thirteen nations. It is 
legalized in the United States by special Act of Congress 
passed in 1866. The English foot is only in use in 
Great Britain, Russia, and the United States. 
4. It is used by scientists in all countries. 
5. It is used exclusively by the U. S. Coast Survey, 
the U. S. Marine Hospital Service, and the U. S. Navy. 
Also by a large number of physicians, especially in 
the north and northwestern sections of our country. 
Other arguments might easily be adduced, but as this 
is not intended to be an exhaustive article, I rest here. 
Objections to introduction of the metric system in the 
United States. 
t. It revolutionizes existing weights and measures. 
2. It is difficult, I might say well-nigh impossible for 
established physicians to forget the old system. 
As to the first of these, each person must weigh the 
arguments pro and con and decide for himself. In my 
opinion, the "game is worth the candle." 
As to the second objection, older physicians should 
not be expected to make the change, unless, indeed, 
they be teachers. But all students should be taught, 
and should learn the new system exclusively. 
In this way a revolution may be accomplished without 
doing violence to any one's principles. 
D. Webster Prentiss, M.l). 
1224 NINTH STKHKT, N. W., 
WASHINGTON, I). C.