. The microscope; an introduction to microscopic methods and to histology. Microscopes. iS6 PARAFFIN SECTIONING \CH. VII cools on the bottom, or a stratum of the paraffin may be cooled on the bottom before putting the tissue in the box. Cool quickly after the tissue is in Fig. 156. Paraffin re- ceptacle P, -with water bath and spout for par- affin imbedding^ iSSj). \ 2S8. Cutting the Sections.—After the imbedding mass is well cooled, re- move the paper box and trim the end containing the tissue in a pyramidal form, clamp the block of paraffin in the holder of the microtome so that the
. The microscope; an introduction to microscopic methods and to histology. Microscopes. iS6 PARAFFIN SECTIONING \CH. VII cools on the bottom, or a stratum of the paraffin may be cooled on the bottom before putting the tissue in the box. Cool quickly after the tissue is in Fig. 156. Paraffin re- ceptacle P, -with water bath and spout for par- affin imbedding^ iSSj). \ 2S8. Cutting the Sections.—After the imbedding mass is well cooled, re- move the paper box and trim the end containing the tissue in a pyramidal form, clamp the block of paraffin in the holder of the microtome so that the tissue will be at the proper level for cutting. If a ribbon microtome is used, heat the holder and melt the end of the block upon it. Cool and place the holder in its place in the microtome. Use a very sharp, dry razor for cutting the sections. The sections are made with a rapid, straight cut as in planing. Do not try to section with a drawing cut as in collodion sectioning. If the temperature of the room is right for the paraffin used, the sections will remain flat, and if the opposite sides of the block are parallel, and one edge strikes the knife squarely, the sections will adhere and thus make a ribbon. If the room is too cold for the paraffin the sections will roll. If it is too warm the sections will crumple. Remember the sections must be very thin, from yi to 15/; to show fine struc- tural details to good advantage. The secret of making good ribbons of sections is to have the block of paraffin containing the tissue cut square and properly arranged in the microtome so that the block strikes the edge of the section knife at right angles with the edge ; and finally the paraffin must be of a proper melting point for the room in which the sections are to be cut. Remember that the larger the object the thicker must be the sections, and the softer the paraffin. Frequently one may modify the tem- perature if too cold by a Bunsen burner flame near the microtome. If it is too wa
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