This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Pinguedo five adeps: Sevum ovillum & hircinum, Axungia porcina & viperina. Animal fats: sheeps suet, goats suet, hogs lard, and vipers fat.
The medical use of these substances is wholly external, as the basis of ointments and other unctuous applications. In their effects, they do not seem to differ materially from one another; all of them having one common emollient virtue, supplying and relaxing the part to which they are applied, and obstructing its perspiration. The principal difference to be considered in them is that of their consistence, by which they are adapted to different forms,. or for receiving different admixtures; the solid feva serving to give the thick consistence of an unguent to oils and the more fluid resinous juices, while the softer axungiae procure a like consistence to solid resins and powders. The fat of the viper is commonly preferred to the others in affections of the eyes; but its superiority, in these cases, to other soft fats, does not appear to have been sufficiently determined by experience. Nor indeed does it appear, that animal fats, and flavourless vegetable oils, of similar consistences, are materially different, respectively, from one another, in their effects when used in external applications. Even in regard to qualities, more remote than those, by which they can act when applied to the external parts of the body, the difference between the vegetable and animal fats is, perhaps, less than might be expected, and apparently less than that which is observed between the other corresponding substances of the two kingdoms, as the gelatinous matters of the one and the gummy of the other: animal fats, in their resolution by fire, yield neither the peculiar stench, nor the volatile alkaline salt, which substances completely animalized afford.
Lard and suet are directed to be tried or purified, by chopping them into small pieces; melting them by a gentle heat, with the addition of a little water, which secures them from any danger of burning or turning black, this fluid not being susceptible of a degree of heat sufficient for that effect; and then (training them from the membranes. Vipers fat, separated from the heart, liver, and other bloody parts, is ordered to be melted without addition, and then strained through a linen cloth; the quantity of this fat, usually purified at a time, being so small, that the heat may be easily regulated, so as to prevent burning, without water.
Tried lard is formed into an elegant ointment, commonly called pomatum, by beating it with rosewater, in the proportion of three ounces of the water to two pounds of the lard, till they are well mixed; then melting it over a very gentle fire, and after standing for a little while, that the watery part may settle, pouring off the lard, and incessantly stirring and beating it about till it grows cold, so as to reduce it into a light yielding mass; and afterwards adding so much essence of lemons as will be sufficient to give a grateful smell. Some scent it with oil of rhodium; and previously digest the lard for ten days with common water, renewing the water every day, a process which does not appear to be of much use. These ointments may be tinged of a fine red colour, for lip-salves, by a proper addition of alkanet root: the faculty of Paris directs, for this purpose, twenty-four parts of the white pomatum, eight of oxes marrow, and eight of white wax cut in small pieces, to be melted together by the heat of a water bath; one part of powdered alkanet root to be added; the mixture stirred at times till it appears tinged of a deep red colour, and then strained through a linen cloth.
Adipis fuillae fevique ovilli curatio Ph. Lond.
Unguentum adipis fuillae Ph. Lond.
Pomatum rubrum Ph. Paris.
Animal fats are not dissoluble by spirit. of wine any more than by water: when scented with essential oils, the oil may be totally extracted by digestion in rectified spirit, so as to leave the fat inodorous. By the same men-struum, fats may be freed from their ill smell, and even those that have grown considerably rancid by keeping may be made sweet again as at first; the rancidity and smell seeming to consist in a part of the fat attenuated, or subti-lized, into a state analogous to that of the oil into which fats are resolved by distillation, which oil is totally dissoluble in spirit.