The solution of the triple sulphate of alumine, (alum of commerce) is employed with the same advantages; it must be confessed, however, that they are more proper to preserve membranous parts which have been previously allowed to macerate a long time. In general, this liquor discolours the parts, and deposits at length on the sides of the jar and the surface of the piece which it bleaches, the white earthy matter with which it is charged; this is a great objection, and exacts great care when the atmosphere freezes suddenly. Chaussier has latterly proposed the solution of the deuto-chloride of mercury, in distilled water. This liquor is very useful, but it bleaches the surface of the parts, particularly the muscles; it hardens, and attacks the instruments when new researches are attempted, upon parts already prepared. This discovery, however, is very valuable to obtain the mummification of certain parts, which it is intended to preserve in the open air. In order to obtain a solution always equally saturated, Chaussier,[12] has proposed to keep at the bottom of the liquor two or three knots of fine linen enclosing a certain quantity of this metallic salt, in order that the saturation may always be complete. [12] See Bulletin des Sciences, by the Philomatic Society, Vol. 3, 6th year, No. 3. In general, we repeat, these preservative liquors are attended with the great inconvenience of leaving suspended, after frosts, the albuminous matters which the cooling has caused to precipitate; so that the fluid of the vessel which contains the preparation becomes clouded, and no longer permits the object so be clearly seen. Besides, the liquor freezes, and breaks the jar, when the temperature is very low. The volatile oils, from whatever vegetable they may have been extracted, are very proper for the preservation of anatomical objects; they lose at length, it is true, their transparency; they thicken, precipitate to the bottom of the vessel, the animal fluids which exude from the object, which exposes them to corruption. But all these changes are sensible to the eye, and the fault is easily repaired when perceived in time to renew the liquor, which may be afterwards re-distilled. It is never useful to employ these liquids for the preservation of objects loaded with fat, for they dissolve these at length and penetrate them entirely, changing their form and colour. Volatile oils, and particularly turpentine, which is the best, are employed to preserve with the greatest success certain injections, the vehicles of which would be dissolved in alcohol, and all the parts whose vessels have been injected with coloured gelatine; finally, these oils are used in all cases where it is desirable to preserve the transparency of certain membranes, which have been previously dried.