ABSTRACT
After fixation, the tissue must be processed for sectioning, staining and mounting. Since water is immiscible with most embedding media and mountants, and yet is the favoured diluent for most stains, tissues must be exchanged between these polar and organic reagents via a series of dehydrating and transition media. Good sectioning requires specimens to be embedded in media of approximately equal density and resilience, so that adequate support is given, and the tissues do not separate under the force of sectioning. Several embedding media have been developed to meet the needs of biological workers. Short ribbons may be placed directly onto a water bath for mounting single sections. In temperate climates wax blocks will keep indefinitely. Some workers prefer to coat the faced block by dipping briefly into hot paraffin wax before storage. The ubiquitous paraffin wax has four important disadvantages which necessitate the use of resins.
