I have obtained the best results by making the Van Gieson’s mixture by taking an ordinary small staining-dish nearly full of saturated water solution of picric acid, and adding to this, drop by drop, sufficient saturated water solution of acid fuchsin to make the solution just dark enough so that the finger cannot be seen through the staining-dish. The hæmatoxylin-stained section is put into this mixture for a few seconds, until it appears to become lighter. The section is then washed in 95 per cent alcohol, dehydrated, cleared and mounted. The Van Gieson method is extremely valuable in pathologic work, because of its varied differential reactions. The nuclei are brown or black, protoplasm is ochre-yellow, connective-tissue light red, voluntary and involuntary muscle yellow, axis-cylinders red, connective-tissue hyalin deep rose-red, epithelial hyalin yellow, orange or brownish, amyloid yellow or brownish pink, mucin yellow or brownish, fibrin yellow or brown, necrotic areas yellow or brownish, lime-salts brown to brownish blue or violet. Combinations of rubin and orange (Delépine) and erythrosin and picric acid (Powell White) are also advised as differential combination stains, but are not so useful as Van Gieson’s. Other combination methods are to be found in the various modifications of the Ehrlich triple stain. CHAPTER XXVI. SPECIAL STAINING METHODS FOR DEMONSTRATION OF PATHOLOGIC CONDITIONS IN CELLS OR TISSUES. =I. AMYLOID.= The best selective staining of amyloid is obtained with relatively fresh tissues; long preservation in alcohol or formol tends to weaken the reactions. Probably the best effects are obtained by formol-fixation for 24 hours, and sectioning on the freezing-microtome. Good results may be produced, however, after any of the ordinary fixing and hardening methods by cutting the sections on the freezing-microtome, without imbedding, or imbedding in paraffin. The metachromatic reactions are not satisfactory with celloidin sections. With hæmatoxylin and eosin the amyloid substance stains a light red or bluish-pink; Van Gieson’s stains it a yellow or brownish-pink color, giving it practically the same color that it does epithelial hyalin. The different tissue-relations of the two substances serve to distinguish them. The most important specific amyloid stains are:— 1. =Iodine.= 1. Stain in Lugol’s solution 5-10 minutes. 2. Dehydrate in absolute alcohol 4 parts, tincture of iodine 1 part. 3. Clear and mount in origanum oil. Seal preparation with paraffin, gold size or shellac.