Optimizing specimen processing for ancient soft tissue specimens

Despite many reports concerning processing of ancient soft tissues, scant attention has been paid to optimizing procedures for processing soft tissues that have been altered by taphonomic processes. To determine the best procedures, we investigated the rehydration solution, time of exposure to the solutions, fixative solution and exposure to heat. Processes were evaluated based on the minimum section thickness, degree of tissue fragmentation, definition of tissue architecture and penetration of stains. We found that in desiccated samples, tissue architecture was optimized by using Ruffer's solution for rehydration and Schaffer's solution as fixative, because these tissues require water restoration within the tissues due to their compacted character. Heating enhanced penetration of dyes in these specimens, which improved diagnosis. Saponified tissues that had suffered extensive decomposition were more labile and required slow water uptake. The best histological sections were obtained using Sandison's solution followed by fixation with formaldehyde and avoiding heat. To obtain the best results with paleohistological specimens, the procedure must be determined by the condition of the sample and by accounting for the nature of its damage.