There are certain organs which may be injected with solid matters, in order to obtain, in relief, resisting, but coarse, the forms of interior cavities. Such is the injection with the matter which forms the stucco paste, or of fine plaster diluted with gelatinous water, which gives to this salt a greater solidity when it takes its consistency. This gross matter is employed with advantage to render more solid the membranes of certain cavities, in the thickness of which it is desired to search for the nerves. Pure wax does not present the same advantage, because it exacts more heat, and contracts more by cooling, although it is more applicable in case it is proposed to corrode with acids all the fleshy or osseous parts, in order to become acquainted with the real form of their interior capacity: in fine, the fusible metallic mixture of Darcet is employed under different circumstances, but it is not more useful.[11] [11] M. Dumèril, work cited. Preservative injections, which may also be applied to vessels and to hollow organs, are composed of materials to which have been attributed preservative properties to the tissues: such are the solutions of mercurial salts, arsenical, ferruginous, &c., and different aromatic and spirituous liquors. _d._ _Ablutions_.--These vary according to the end proposed: acids; these serve to give whiteness to some tissues and resistance to others: alkaline; these clean the preparations, divesting them of the mucilage and grease which they contain. In one word, the action of aqueous liquids, of oily, alkaline, saline, acid, alcoholic, is necessary before, as well as after dissection to preserve the preparations. When these preparations are left a longer or shorter time in water, they are subjected to what is called a _degorgement_; the bath ought to be renewed until it will no longer receive any colouring matter. The removal of _grease_ is included under dissection, maceration, and ablution. _e._ _Ligature of the vessels._--This is made with a flat silk, or silk very slightly twisted, during the dissection, or immediately after, on the extremity of the vessel which contains the injection; it is necessary in order to prevent the escape of the injected matter. _f._ _Separation and distention of parts._--These offer the whole surface of the prepared pieces to those agents of preservation which ought to be applied to them; they sustain them, and preserve them from being deformed. Besides, it is well known, that the means of separation and distension ought to vary according to the form of the organs; atmospheric air suffices for hollow and thin organs, the stomach, the intestines, the bladder, &c. Under other circumstances, wool, hair cotton, plaster, &c., serve better. SECT. 2.--_Means of Preservation._