568 
LECTURES ON THE BRITISH PIIARMACOPCEIA. 
longer digestion at a lower temperature would do as well. In confirmation of 
the deduction from these experiments that a moderately high temperature does 
not injure the active principle of cantharides, but that its natural volatility is 
retarded by dissemination through fatty matters, and only accelerated when escap¬ 
ing vapour of water, etc., carries it away, Southall states (Pharm. Journ. vol. ii. 
p. 655) that on evaporating an infusion of cantharides, he was attacked by in¬ 
flammation of the eyes so severely as to be confined at home for two or three 
days ; and that, subsequently, he was still more severely affected on stirring 
soft plaster into some wax that had been melted over a naked fire. Finally, 
Proctor, of Philadelphia, in an elaborate paper on the volatility and solubility of 
cantliaridin (Amer. Journ. Pharm. 1862, and Pharm. Journ. vol. xii. p. 291) 
says, “When powdered flies are stirred into the ordinary vehicle of resin, wax, 
and lard, so as to chill it almost immediately, but little of the cantharidin is dis¬ 
solved by the fatty matter, and when applied to the skin the process of vesica¬ 
tion is retarded. If, however, the cerate be kept fluid for a length of time, say 
for half an hour, by a water-bath or other regular heat, no loss of cantharidin 
occurs by the heat, the active principle is in great measure dissolved by the fat, 
and every part is impregnated and active.” In face of these researches we are 
told to do exactly what they indicate should not be done. We can only suppose 
that in this matter the authors of the British Pharmacopoeia have committed the 
grave error of not searching any pharmaceutical or chemical journals for papers 
on this subject since the last three Pharmacopoeias were published. 
Emplastrum Opii. This is a very different plaster to that of the last London 
Pharmacopoeia, but somewhat resembles the Edinburgh form. It is the Dublin 
process, and'contains in the place of the extract of opium of the London College 
powdered opium, as was suggested for the London Pharmacopoeia by Southall 
(Pharm. Journ. 2nd ser. vol. i. p. 11); and, in place of frankincense, resin, as sug¬ 
gested for the London form by Haselden (Pharm. Journ. 2nd ser. vol. i. p. 545). 
Extracta. —I feel strongly inclined to pass over the subject of medicinal 
extracts, for I must confess I scarcely know where the stand-point should be from 
which to examine the processes given for their preparation in the British or any 
other Pharmacopoeia. Some are concentrated juices, others concentrated infu¬ 
sions, others concentrated decoctions, others concentrated tinctures of plants, of 
whose general constituents little or nothing, and of whose special constituents 
still less, may be known. Excepting any changes that may be effected during 
evaporation, they may therefore, from a therapeutical and chemical point of view, 
be classed with juices, infusions, decoctions, and tinctures ; their only distinctive 
value being that they offer to the medical practitioner a means by which either 
of those four classes of preparations can be given in a solid, that is, a pilular, 
form. If this be their true position as remedial agents, they, unlike other gale¬ 
nical compounds, need only to be considered from a purely physical point of 
view. And, so far as I have observed, those published investigations and sug¬ 
gestions of pharmaceutists which have had reference to improvements in the 
consistence, persistence, and other physical conditions of extracts, seem in several 
instances in the British Pharmacopoeia to have been attended to. 
The extracts of Aconite , Belladonna , Hemlock , and Henbane , still will contain 
any starchy matter pressed out with the juice of the fresh leaves and young 
branches of the plants. So far these extracts will resemble those of the London 
Pharmacopoeia, but to exactly the same extent will differ from those of the 
Edinburgh and Dublin Pharmacopoeias, both of which ordered that amylaceous 
matter should be rejected either b} r filtration or subsidence. It is to be hoped, 
therefore, that in the course of a year or so Scotch and Irish pharmaceutists will 
publish their experience of the extent to which this retention of starch has 
affected the physical qualities of the extracts they have been in the habit of dis¬ 
pensing. These extracts, as well as those of Colchicum , Liquorice , and Taraxacum , 
