. The microscope : an introduction to microscopic methods and to histology. Microscopes. 294 PARAFFIN METHOD ICH. X Nearly fill the box with paraffin wax,' place on a copper heater (Fig. 241) and allow to remain until bubbles appear in it. Put the box on cold water until a thin stratum of paraffin solidifies on the bottom. Take the piece of tissue from the melted paraffin (Fig. 230) and arrange in the box for making sections in a definite direc- tion. Add hot paraffin if necessary, and then place the box on cold water. The more rapid the cooling the more homogeneous will be the block containin
. The microscope : an introduction to microscopic methods and to histology. Microscopes. 294 PARAFFIN METHOD ICH. X Nearly fill the box with paraffin wax,' place on a copper heater (Fig. 241) and allow to remain until bubbles appear in it. Put the box on cold water until a thin stratum of paraffin solidifies on the bottom. Take the piece of tissue from the melted paraffin (Fig. 230) and arrange in the box for making sections in a definite direc- tion. Add hot paraffin if necessary, and then place the box on cold water. The more rapid the cooling the more homogeneous will be the block containing the tissue to be cut. For the best imbedding it is well to drop 95% alcohol on the surface as soon as a film has formed in cooling. In warm climates where cold water is not easy to procure for cooling the blocks, one may float the paper box on 95,% alcohol and w'ith a pipette (Fig. 240) drop strong alcohol on the sides of the box and on the top of the paraffin as soon as a sur- face film has formed. It is very desirable to mark on the box the name of the imbedded object and to indicate which end or face is to be cut. See also under serial sectioning (§ 472-473). Fig. 232. Various forms of scalpels. The one at the left is especially excellent for cutting the ribbons of sec- tions of the proper length for mounting. The large one with straight edge is the best form for trimming the paraffin block square for sectioning. {Cut loaned by the Bausch & Lomb Opti- cal Co.) § 442. Fastening the Block to a Holder.—Use one of the block holders or object discs furnished with the microtome, or a short stove bolt (Figs. 233-236). Heat the larger end and press the paraffin block against the hot metal until it melts the paraffin. Hold the two together while cold water flows over them. When cold the block is firmly cemented to the holder. Pains should be taken to have the axis of the block parallel with the long axis of the holder; and one should not cut the block so short that th,e hol
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