SUMMARY Dimensional changes of bovine kidney and liver tissues in the course of processing under four different schedules were measured. Shrinkage of tissues at dehydration, substitution with intermedium and paraffin infiltration stages was 1–2%, 2–5% and 5–10% respectively. There was no significant difference in final dimension and morphology among the specimens processed under the different schedules. Any one of the investigated schedules can be employed for practical tissue processing. For many years, biologists' attention has been paid to swelling and shrinkage of tissues in the course of specimen preparation for microscopy. Morphometric changes of tissues throughout specimen preparation for EM were discussed by Kushida (1962) and Hansdete & Gerrits (1983). Bahr et al. (1957) precisely measured changes of volume, weight and specific gravity of several organs of guinea‐pigs during fixation and subsequent processing. Lee et al. (1980) described dimensional changes of specimens at the stages of plastic monomer infiltration and polymerization. A morphometric study from fixation through cutting of cervical tissue by Boonstra et al. (1984) appears in a current journal. Further, effects of lithium salts as additives and 2,2‐dimethoxypropane as a dehydrant on dimensional stabilization at dehydration stage were reported by Boyde & Maconnachie (1980) and Truter et al. (1979) respectively. While there have been the above‐cited studies, it appeared of interest to investigate further dimensional changes of tissues with the passage of time at each stage of processing. As precise determination of tissue dimensions and comparison of shrinkage under various conditions seemed of importance, we have devised a rational processing schedule for optical microscopy.

Development of a resin-dissolving solution for use at low alkali concentrations is described. Crown ether dissolved in dimethyl-sulfoxide produces a superbasic alkoxide anion. A five minute treatment resulted in complete resin removal from kidney biopsy specimens embedded in Epon 812. Specimens were well stained by Loeffler's methylene blue. Periodic acid-methenamine silver and Giemsa stains yielded good results. Application of PAS reaction and subsequent hematoxylin counterstaining was practicable for diagnosis.

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