6. =Acetic Acid Fuchsin.= A few drops of fuchsin are added to a 2 per cent solution of acetic acid. With this solution the nuclei are not only brought out more sharply but they are stained red. 7. =Lugol’s Solution.= Dilute Lugol’s solution to a pale yellow color. It brings out the contours of cell and nucleus, and has a specific reaction with glycogen and amyloid, giving both a brown color. Since glycogen is dissolved out in water-solutions tests for glycogen in fresh tissues should be made with iodine-glycerin or iodine-gum (Lugol’s one part, gum arabic 100 parts). Smears or cover-glass preparations may be placed in covered dishes containing a few crystals of iodine. 8. =Potassium and Sodium Hydroxides.= In solutions of 1-3 per cent all tissue-structures swell and dissolve or become unrecognizable except elastic fibres, fat, pigment, amyloid, bacteria, yeasts and moulds. Used especially for examination of skin-scrapings or pus for presence of blastomyces and various forms of parasitic moulds (barber’s itch, ringworm, tinea, etc.). Solutions of 33 per cent clear the tissues but do not destroy the cells. Useful for maceration. When diluted the cells are destroyed. 9. =Mineral Acids.= HCl or H_{2}SO_{4} (3-5 per cent). Used to dissolve areas of calcification. Calcium dissolves with liberation of CO_{2}; the phosphates dissolve without gas-formation, but with H_{2}SO_{4} form crystals of calcium sulphate. Sulphuric acid is also used as a test for cholesterin (red or violet coloration), and with iodine as a test for amyloid. 10. =Osmic Acid.= In a 1 per cent solution this is used to test for the presence of fat (oleates), the fat-droplets become black or brown. 11. =Sudan III or Scharlach R.= Alcoholic solutions of these dyes are used for the demonstration of fat in fresh tissues. They stain fat orange to scarlet. (For method see Staining of Fat.) 12. =Alcohol and Ether.= Used to dissolve fat-granules and to differentiate between these and albuminous granules. 13. =Stains.= Fuchsin, methylene blue, methylene green in 1 per cent solutions in physiologic salt-solution and acetic-acid-fuchsin are the best stains used for the examination of fresh-tissues beneath the cover-glass. They are drawn under the cover-glass according to the method given above.