472 
LECTURES ON THE BRITISH PHARMACOPOEIA. 
improvement upon the old one, for by straining the decoction after it has 
cooled, it is obtained in a comparatively clear state. Still, however, it is 
subject to the formation of a slight precipitate after standing for some days. 
I may remark, with reference to this decoction, that the boiling of the bark 
with water, as directed, extracts rather less than one-half of the quinine that 
is contained in the bark ; and if the residual bark, after being thus used, be 
boiled with water acidulated with sulphuric or hydrochloric acid, it will yield 
the remainder, amounting to about six or seven grains of the alkaloid from 
an ounce of bark. 
But the most important changes in the decoctions are those which relate 
to the means of ensuring uniformity of strength and other properties in the 
products. Our processes hitherto have been very deficient in the means pro¬ 
vided for this purpose. Thus, in the London Pharmacopoeia the general in¬ 
structions are either to boil until the decoction is reduced to a certain mea¬ 
sure, or to boil for a certain space of time, usually ten minutes. Both these 
methods are liable to yield variable results, according to the quantities ope¬ 
rated upon, and the form of the vessel in which the decoction is made. It is 
quite obvious that if I were making half a pint of decoction in a vessel pre¬ 
senting a large surface to the fire, I might boil it all away in ten minutes ; 
whereas, if I were operating upon two or three gallons, I should effect but a 
comparatively small reduction of volume in the liquid in that time. So also, 
if I had to reduce nine ounces of liquid to six ounces by boiling it, I could do 
so in a few minutes; but if I had to reduce nine gallons to six gallons, it 
would be necessary to boil it for a much longer time, and under these cir¬ 
cumstances the ingredients would be subject to a much longer application of 
the boiling process in the one case than in the other, so that the products 
would be likely to vary in their characters. 
Now, some attempt has been made in the new Pharmacopoeia to remedy 
these defects. In the process for compound decoction of aloes, and also in 
that for decoction of bark, instructions are given which appear to be unex¬ 
ceptionable. We are directed to boil the solid ingredients for a specified time 
(ten minutes) with a quantity of water that w r ould not under any circumstances 
yield the full amount of decoction required, and then, after straining this, the 
quantity specified is to be made up by pouring water over the ingredients in 
the strainer. 
After having thus adopted so excellent a process for two of the decoctions, 
it seems extraordinary that the same method should not have been applied to 
other similar preparations. "Why, for instance, should it not be applied to the 
preparation of the decoctions of poppies, sarsaparilla, and taraxacum. It is 
true that we are told in the instructions for making those decoctions that 
the ingredients are to be boiled for ten minutes, and that the product is to 
be made up to a specified quantity ; but we are not told to make up the pro¬ 
duct by the displacement of the liquid retained in the marc, and as the loss in 
boiling will vary according to the quantity operated upon, if the product is 
made up in any other way than by displacement, the product will be sub¬ 
ject to variation. 
JEmplastra .—The number of plasters is reduced from fourteen to twelve, 
three being omitted and one added. There are some alterations in several of 
those that are retained, and these appear to be improvements. 
JSnemata .—With reference to these I have little to remark beyond what 
the tables indicate. The number is unchanged, one being omitted, and 
one added, while the others are altered in strength or composition. 
JExtracta .—The medicinal extracts are a very important class of prepara¬ 
tions, containing, as they do, the active constituents of many powerful drugs, 
which are often administered in a concentrated state. The processes for the 
