46. _Tongue._—Harden in chromic acid, imbed and cut transverse sections in paraffine. As, however, the paraffine is apt to get entangled amongst the _papillæ_, whence it is afterwards with difficulty dislodged, it will be as well before imbedding to soak the tongue in strong gum for a _few minutes_, and afterwards immerse in alcohol till the gum becomes hardened, so that the delicate papillæ may thus be protected from the paraffine by a surface-coating of gum. The best staining agent is picro-carmine (§ 42). Sections of _cat’s_ tongue near the root, when thus stained, furnish splendid objects. Sections should also be made of the _taste-bulbs_, found on the tongues of rabbits. These are small oval prominences, situated one on each side of the upper surface of the tongue near its root. They should be snipped off with scissors, and vertical sections made in the direction of their long axis. Stain with carmine or picro-carmine, and mount in glycerine or balsam. 47. _Vegetable Ivory_.—After prolonged soaking in cold water may readily be cut in the microtome. The sections should be mounted in balsam, and though not usually regarded as polariscopic objects, nevertheless, when examined with the _selenite_, yield very good colours. 48. _Wood._—Shavings of extreme thinness may be cut from large pieces or blocks of timber, by means of a very sharp plane. In this way very good sections may be procured of most of the common woods, as oak, mahogany, “glandular wood” of pine, etc. Where however, the material to be operated upon takes the form of stems, roots, etc., of no great thickness, they should, after having been reduced to a suitable consistence (§ 4), be imbedded in paraffine, and cut in the microtome. Before imbedding it must not be forgotten to immerse the wood to be cut in weak gum-water (§ 11), this precaution being of great importance, especially in the case of stems, etc., the bark of which is at all rough and sinuous. If the sections are to be mounted _unstained_, they are usually put up in weak spirit (§ 26). A very general method also of dealing with this class of objects is to mount them _dry_ (§ 26). This plan, however, cannot be recommended, for however thin the sections may be, the outlines, when this process is adopted, always present a disagreeable black or blurred appearance. To avoid this we may have recourse to Canada balsam, but the ordinary method of employing it must be slightly modified, a drop of chloroform being substituted for the clove oil (§ 23), otherwise this latter agent will cause the section to become so transparent as to render minute details of structure difficult to recognize. A better plan, perhaps, is to stain the section with carmine or logwood, and mount in balsam by the ordinary process. The best course to follow, however, especially in the case of transverse sections, is the _double staining_ method.[18] For this purpose the sections in the first place must be subjected to the action of a