To prepare _serial-sections_ from celloidin blocks the sections as they are cut must be arranged in their order on the knife-blade and thence transferred in this order to a slide or glass-plate, to which they are either fastened so that they cannot become loose during the staining process, or they are fastened together by a film of celloidin and stained in one piece. To fasten the celloidin sections to the slide _Mallory_ and _Wright_ suggest the cutting of the block in 95 per cent alcohol, and the arrangement of the sections in their order on the knife, whence they are drawn on to a dry, clean and numbered slide. Ether vapor from a half-full bottle of ether is then poured over the slide, slowly, to flatten out the sections and fasten down the frilled edges. The slides are then transferred to 80 per cent alcohol to harden the celloidin, and they are kept in this solution until ready for staining. Celloidin sections may also be fastened to the slide by albumin glycerin (equal parts white of egg and glycerin with a crystal of phenol or thymol). The celloidin sections, as they are cut, may be transferred to a dry gelatinized slide or plate (16 grms. gelatin in 300 cc. warm water), and are then covered with a thin celloidin; the slide is then placed in water at 50°C., the gelatin dissolves and the celloidin film floats off; the latter is then stained as one section. Serial sections of celloidin-blocks may also be arranged upon slides or plates covered with a coating of the _Schmorl-Obregia_ sugar-dextrin solution or diluted New Orleans black molasses; the slide or plate is flooded with absolute alcohol; drained; a thin celloidin is then poured over it; it is immersed in warm water and the celloidin-sheet containing the sections is liberated, and is then stained as a whole or cut into strips as desired. The molasses method is the cheapest and simplest method, and much to be preferred to the Weigert closet-paper method, by which the sections are arranged upon a strip of moist closet-paper which is either held upon the slide or kept upon a piece of blotting-paper wet with 80 per cent alcohol. A slide or glass-plate is covered with a thin layer of celloidin and the strip of paper containing the sections is laid upon the celloidin surface, the sections down, so that these stick to the slide as the paper is carefully peeled off. The preparation is dried with filter-paper and a thin layer of celloidin poured over the slide and sections. The celloidin is then hardened in 80 per cent alcohol and the sections stained on the slide; or the celloidin film is removed by immersion in warm water, and then treated as one section. Celloidin films may be marked with a brush dipped in a water solution of methylene-blue. This should be done as soon as they are made. _Langhans’ method_ is advised for the remounting of serial sections from tissues stained in bulk and imbedded in celloidin. The sections are cut in