A Modified Freezing-Drying Apparatus for Tissues

The preparation of tissues by the freezing-drying technic is preferred for many histochemical studies because of the rapid fixation, avoidance of deleterious action of chemical fixation and extraction by aqueous and lipid solvents in fixation, dehydration and clearing; to facilitate this procedure a freezing-drying apparatus has been constructed which permits cutting of sections within five hours after the fresh tissue is obtained. Liquid nitrogen provides a most efficient moisture trap and in conjunction with a heating element provides any desired temperature down to — 80°C. during tissue drying. Paraffin infiltration is started without disassembling the equipment and completed in a few minutes. Most stains and histochemical reactions for enzyme and other substances can be applied directly to sections of frozen-dried tissue cut from the same blocks.