Chap. XLI.

Of Liniments, <$r.

635

linen on which the plaster has been laid, through a machineformed of a spatula fixed, by screws, at a proper distancefrom a plate of polished steel.

To prevent repetition, the Edinburgh college give the fol-lowing canon for the preparation of these substances :

In making these compositions, the fatty and resinous substan-ces are to be melted with a gentle heat, and then constant-ly stirred, adding, at the same time, the dry ingredients,if there be any, until the mixture on cooling becomes stiff.

The Dublin College prefixes the following direction :

Tutty and calamine employed in making ointments, are pre-pared in the same manner as chalk.

In making ointments and plasters, the wax, resins, and fats,are to be melted with a moderate heat, then removed fromthe fire, and constantly stirred, until they cool, adding, atthe same time, the dry ingredients, if there be any, in veryfine powder.

Sevum prjeparatum. Lond.Prepared Suet.Cut the suet into pieces, melt it over a slow fire, and expressit through linen.

Adeps prjeparata. Lond.Prepared Hogs Lard.Cut the lard into pieces, melt it over a slow fire, and expressit through linen.

Adeps sujixus pr^pakatus. Dub.

Prepared Iiogs Lard.

Melt fresh lard, cut in pieces, with a moderate heat, and strain

with expression through flannel.Lard, which is purified by those who sell it, and which ispreserved with salt, is to be melted with twice its weight ofboiling water, and the mixture well agitated. Set it thenaside until it cool, and separate the fat.

Before proceeding to melt these fats, it is better to sepa-rate as much of the membranes as possible, and to wash themin repeated quantities of water until they no longer give outany colour. Over the fire they will be perfectly transparent,and, if they do not crackle on throwing a few drops into thefire, it is a sign that all the water is evaporated, and that the

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