Ointments differ from plasters only in their consistence : those prepared of animal fat appear to be more congenial to the human sys-tem, than such as are compounds ed with vegetable oils ; though the formes: former are more liable to become -rancid by long keeping, and ought, therefore, to be applied when in a fresh state.
In the preparation of ointments, the fat and resinous substances ought first to be melted in a-gentle heat, over, which they should be carefully stirred, when such dry ingredients as may be necessary (being finely pulverized), must be gradually sprinkled in; till, on di-. minishing the heat, the mixture become stiff.
Simple Ointment consists of five parts of olive-oil, and two parts of white-wax, thoroughly incorporated.
Ointment of Hog's-lard is prepared by triturating two pounds of hog's-lard with three ounces of rose-water, till they are perfectly mixed. The whole should now be melted over a moderate fire, and suffered to subside, when the lard must be poured off, and constantly stirred, till it become cold.
Both these ointments may be used for softening the skin, and healing chaps. The former, however, being of a more uniform consistence, is preferable to the latter : but too large a quantity of either ought not to- be prepared at one time ; because, when they have, been kept for some months, or even a few weeks, they lose their healing properties.
Van Mons has devised a new, and less troublesome, method of compounding ointments and plasters, in which fresh herbs, or their expressed juices, are employed as ingredients. The vegetable sap ought previously to be strained, and deprived of all feculent matters : next it is placed over a very moderate fire, in a shallow earthen Vessel, where it is evaporated nearly to -dryness : this coagulated extract is now baked or dried in an oven, so that it may be reduced to powder; in which state it is again exposed to the fire, together with the fat or oil intended for its vehicle, till the humidity is completely evaporated.- For a cheap and useful family ointment, see BURNS, vol. i. p. 398.