pear. As soon as this is the case, it is ne- 
cessaiy to mix with the mass a proportion 
of some dry powder, to give it a proper 
degree of consistency. For this purpose 
powder of liquorice root has been com- 
monly used ; but it is extremely apt to be- 
come mouldy, and to cause the pills to 
spoil. The Edinburgh College have, tliere- 
fore, with great propriety, substituted for 
, its starch, which is a very inalterable sub- 
stance, and easily procured at all times in a 
state of purity. It is necessary to form the 
mass into pills immediately, as it soon be- 
comes hard. One grain of mercury is con- 
tained in four grains of the Edinburgh mass, 
in three of the London, and in two and a 
half of the Dublin. The dose of these pills 
must be regulated by circumstances ; from 
two to six five-grain pills may be given 
daily. 
Class XXIV. Cataplastnaia. Cataplasms. 
By cataplasms are generally understood 
those external applications which are brought 
to a due consistence or form for being pro- 
perly applied, not by means of oily or fatty 
matters, but by water or watery fluids. Of 
these many are had recourse to in actual 
practice ; but they are seldom prepared in 
the shops of the apothecaries, and in some 
of the best modern Pharmacopoeias no for- 
mula of this kind is introduced. The Lon- 
don and Dublin Colleges, however, although 
they have abridged the number of cata- 
plasms, still retain a few ; and it is not 
without some advantage that there are fixed 
forms for the preparation of them. 
Cataplasma aluminis. Loud. Coagulum 
aluminis, Dubl. cataplasm of alum, alum 
curd. 
Cataplasma cumini. Lend, cataplasm of 
cummin, London treacle. 
Cataplasma sinapeos, Lond. Dubl. cata- 
plasm of mustard. 
Cataplasms of mustard are commonly 
known by the name of sinapisms. They 
were formerly frequently prepared in a more 
complicated state, containing garlic, black 
soap, and other similar articles; but the 
above simple form will answer every purpose 
which they are capable of aocomplishing. 
They are employed only as stimulants : they 
often inflame the part and raise blisters, 
but not so perfectly as cantharides. They 
are frequently applied to the soles of the 
feet in the low state of acute diseases, for 
raising the pulse and relieving the head. 
The chief advantage they have depends on 
tlie suddenness of their action. 
Class XXV. hinimenta. Liniments. 
Class XXVI. Unguenta. Ointments. 
Class XXVII. Cerata, Cerates. 
Class XXVIII. Emplastra. Pl.asters. 
Weconnect these together as being all ole- 
aginous or fatty combinations for external ap- 
plication, and as merely differing from each 
other in their degree of consistency. De- 
yeux has, indeed, lately defined plasters to 
be combinations of oil with metallic oxides ; 
but as this would comprehend many of onr 
present ointmentSj and exclude many of our 
plasters, we shall adhere to the old meaning 
of the terms. 
Liniments are the thinnest of these com- 
positions, being only a little thicker than oil. 
Ointments have generally a degree of 
consistence like tliat of butter. 
Cerates are firmer, and contain a larger 
proportion of wax. 
Plasters are the most solid, and when 
cold should be firm, and not adhere to the 
fingers ; but when gently heated should be- 
come sufficiently soft to spread easily, and 
should then adhere to the skin. Plasters 
derive their firmness either from a large 
proportion of wax, resin, &c. or from the 
presence of some metallic' oxide, such as 
that of lead. 
Plasters should have such a consistence, 
that although when cold they do not adhere 
to the fingers, they become soft and plastic 
when gently heated. The heat of the body 
should render it tenacious enough to adhere 
to the skin, and to the substance on which it is 
spread. When prepared, it is usually formed 
into rolls, and inclosed in paper. Plasters 
of a small size are often spread on leather, 
sometimes on strong paper, by means of a 
spatula gently heated, or the thumb. The 
leather is cut of the shape wanted, but 
somewhat larger ; and the margin all round, 
about a quarter of an inch in breadth, is left 
uncovered, for its more easy removal when 
necessary. Linen is also often used, espe- 
cially for the less active plasters, which are 
used as dressings, and often renewed. It is 
generally cut into long slips of various 
breadths, from one to six inches. These 
may either be dipped into the melted plaster, 
and passed through two pieces of straight 
and smooth wood, held firmly together, so 
as to remove any excess of plaster; or, 
what is more elegant, they are spread on 
one side only, by stretching the linen, and 
applying the plaster, which has been melted 
and allowed to become almost cold, evenly 
