Once fixed, the tissue must be treated to allow the cutting of the thin sections required for viewing under the microscope. The procedures designed to prepare the tissue for sectioning are collectively known as Tissue Processing. First, the sample is dehydrated by immersion in a series of aqueous alcohol solutions gradually moving to pure alcohol. The tissue is then soaked in an appropriate solvent to remove the alcohol. Finally the tissue is embedded in paraffin wax, which enables the cutting of sections of between 3 and 10 microns thickness. The movement through the series of baths in Tissue Processing occurs either by hand or by means of an automated processor. Table 1.3a gives a typical tissue schedule for an automated processor. The optimum protocol for any particular sample and apparatus may vary.

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