1. =Cutting of Fixed Tissues Without Imbedding or Freezing.= It occasionally becomes necessary in pathologic work to cut tissues directly upon the microtome without freezing or imbedding. This can be done satisfactorily in the case of very firm substances, such as amyloid liver and spleen, etc. The sectioning is done in the wet, using 80 per cent alcohol, as in celloidin cutting. A large celloidin knife should be used, and the blade should be flooded in alcohol. A large piece of the tissue, or, better, several pieces, are clamped in the object holder with only a small layer of tissue above the holder. The knife-blade is placed at the least possible angle to the pieces of tissue. To obtain sections of 15-20 microns in thickness the object-holder is raised each time about 25-30 microns. The sections will vary in thickness, some thin, others very thick. 2. =Sectioning of Frozen Fixed Tissues.= Tissues fixed in formol, Müller’s fluid or Orth’s fluid may be frozen directly on the freezing-microtome without previous washing. For other fixations previous washing is necessary. Tissues in alcohol must have the alcohol thoroughly washed out before freezing. Celloidin blocks may also be cut by freezing after the removal of alcohol. The fixed tissues cut to the proper size are placed on the object-holder of the freezing-microtome in a drop of saturated gum-arabic and the freezing carried out as directed above. (See Page 214.) As the freezing causes little or no damage to fixed tissue, the frozen sections may be transferred directly to alcohol, or floated out on the dilute molasses or sugar-dextrin solution, and stained separately or in sheets, according to the directions given in the next chapter. 3. =Sectioning of Celloidin Blocks.= The celloidin blocks are fastened in the object-holder of the microtome, and the knife-blade (a longer and broader one than for paraffin-sectioning is advisable) set nearly parallel with the longitudinal axis of the microtome, so that the cutting-edge, striking the block at a very slight angle, will be utilized for the greater part of its length in cutting entirely across the surface of the block. Both object and knife-blade must be kept constantly wet with 80 per cent alcohol; a broad camel’s-hair brush or a drip-bottle can be used for this purpose. The sections, as they are cut, are transferred from the knife to 80 per cent alcohol by sweeping the finger or brush from above toward the edge of the blade. Care must be taken not to strike the brush against the edge of the blade, and this can be avoided by using the brush always with a downward stroke. As the sections are cut they are guided onto the knife-blade by means of a fine-pointed camel’s-hair brush, if the sections show any tendency to curl. They should be smoothed out at once on the knife, and then transferred to the dish of 80 per cent alcohol. Sections 7-10µ thick are easily cut in celloidin, if the process of imbedding has been carefully carried out.