1. Harden in absolute alcohol; imbed; cut. 2. Stain with saturated water solution of dahlia. 3. Wash in water. 4. Dehydrate in absolute alcohol. 5. Clear in xylol; mount in balsam. _c. Unna’s Method for Mast and Plasma Cells._ 1. Harden in absolute alcohol; imbed; cut. 2. Stain in Unna’s polychrome methylene blue ¼-12 hours. 3. Wash in water. 4. Differentiate in Unna’s glycerin-ether mixture (Grübler) 15 seconds to several minutes. 5. Wash carefully in water. 6. Dehydrate in absolute alcohol; clear in xylol; mount in balsam. Mast cell granules are red; plasma cell granules blue. _d._ Various modifications of the _Romanowsky method_ stain mast- and plasma-cells very well. =XVI. IODINE.= For the demonstration of iodine in tissues the following method has been advised by =Justus=. The experience of other workers with it has not been satisfactory. 1. Harden in absolute alcohol; imbed in celloidin; cut. 2. Soak in water to remove alcohol. 3. Put section in wide-mouthed, stoppered bottle in freshly prepared green chlorine-water for 1-2 minutes. 4. Transfer section on a glass needle to a vessel containing 500 cc. water and 1 cc. of a 1 per cent solution of silver nitrate for 2-3 hours. The section is colored yellow-green, and a precipitate of silver chloride appears. 5. Transfer section to a warm saturated solution of sodium chloride until it becomes light. 6. Wash in distilled water. 7. Transfer to a concentrated solution of mercuric chloride. 8. Examine in pure glycerin. Iodine should be red. =XVII. MITOTIC FIGURES.= Various histologic methods devised for the study of mitoses can be applied to the demonstration of these in neoplasms, inflammation and regeneration. Flemming’s solution or mercuric chloride fixation gives best results, although formol, or even absolute alcohol, when used quickly and carefully gives fair results if tissue is very fresh. 1. =Flemming’s Solution and Safranin.= 1. Fix small pieces of fresh tissue in Flemming’s, in the dark, for 24 hours; wash 24 hours; after-harden in graded alcohols; imbed and cut. 2. Stain in 1 per cent water solution or saturated aniline water solution of safranin, or 1 per cent water methyl violet for 12-24 hours, or carbol-fuchsin for one hour. 3. Differentiate quickly in a 0.5-0.0001 HCl in 70 per cent alcohol and then in absolute alcohol until stain no longer comes away in clouds and nuclei have right shade. 4. Clear in xylol; mount in balsam. Fat is black; mitoses stand out sharply; tubercle-bacilli may be stained black or red.