The place of histochemical techniques in toxicology, pharmacology and pathology

The uses of histochemistry in pathology (experimental and clinical), pharmacology and toxicology are considered and their restrictions are discussed. In time-course studies of drug effects in animals the research worker must choose an appropriate histochemical technique for evaluating the changes seen in the tissues, if any, during the study. Acid phosphatase is shown to be a marker enzyme which may be active in both cell multiplication and tissue necrosis; results obtained with it must therefore be interpreted with caution. The need for histochemical techniques to match experimental conditions is emphasized. The restrictions of fixation and tissue preparation are also emphasized. Histochemical and biochemical techniques should be used together where appropriate, and the results should be analysed carefully. Indiscriminate use of histochemistry and quantitation is deplored.