The mixture of mutton fat or of suet, of white or yellow wax, of the fixed oils of olives, nuts, or flax seed, are the ordinary matters of injections, even for those destined for corrosions. The different degrees of solidity or softness are determined by the calculated proportions of wax and oil, and by the amalgam of resinous and colouring matters. In general, in this sort of injections it is advantageous to introduce beforehand, a small quantity of volatile oil mixed with the fatty matter which is to serve for filling the vessels; by this preliminary process a liquid more fluid, more penetrating, higher coloured, and susceptible of cooling more slowly, is driven before into the smaller ramifications. I could here transcribe several receipts proper to indicate the proportion of fatty matters among themselves; but the season during which the pieces are made, the nature of the ingredients employed on them, will occasion the proportional quantities to vary, so that a sketch only can be given for obtaining a matter which may be made more solid or more fluid after having tried it by cooling some drops separately. Nevertheless, here is one of those receipts: ℞. Of suet, 5 parts. Burgundy pitch, 2 " Oil of olives, or of nuts, 2 " Of fluid turpentine and colouring matter, dissolved in volatile oil, 1 " This latter part should not be mixed until the liquor is well melted and ready to be put into the syringe, as the heat will volatilize the volatile oils, which will become disengaged in the form of gas, and cause the mass to occupy a very great volume. As a matter of injection, the dissolved gum elastic or caoutchouc may be employed; it becomes gelatinized in losing a portion of its menstruum by desiccation. After leaving this matter in a moist place, and having well washed it, in order to clean it of the clayey matter which generally impregnates it, it may be dissolved in volatile oils by heating it in a sand bath, with a moderate fire in a matrass with a long neck; adding by degrees, a sufficient quantity of oil to render the mass very fluid, incorporating with it the colouring matters which have been previously ground in an essential oil. The gum elastic may also be dissolved in ether, but this process is too expensive; and as a matter for injecting this liquor is not preferable to the other. The elastic injections are only advantageous in the preparation of parts which are not to be exposed to cutting instruments, and to which it is desirable to preserve a certain degree of suppleness, as in the injection of the cotyledons, or the placenta of women. This liquor, it must be confessed, has the great inconvenience of retaining its odour a long time, assuming its solid form with difficulty, and of rendering the preparations pitchy, and rebellious to varnish, and becoming loaded with dust.