Metachromasia after treating tissue sections with sulphuric acid.

on the capacity of tissue elements to strain metachromatically. Surprising as it may seem, adequately fixed and dehydrated tissues withstand five minutes' immersion in concentrated sulphuric acid without charring or showing any severe disturbance of their structure. Subsequent staining with a metachromatic dye reveals that a greatly increased range of tissue elements shows a metachromatic affinity, and this staining technique offers a new and useful polychrome method which may well have some degree of histochemical specificity. The technique which has been developed involves immersion of sections in concentrated sulphuric acid, followed by staining with a dilute solution of a metachromatic dye. The method is simple, quick, and reliable.