Mucopolysaccharides and the Calcification of the Scale of the Roach

I . The scale of the roach (Leuciscus rutilus L.) was examined for state of calcification, metachromasy, and reaction to the periodic acid / Schiff (PAS) test. 2. Metachromasy and a positive PAS-reaction imply acid mucopolysaccharides in the bony layer. 3. There is a great increase in these reactions and in reactions for bone salts in the transition zone between the uncalcified and calcified part of the bony layer. 4. These reactions imply that the bond between the osseoid and the inorganic fraction of the bony layer is through SO2and PO4-groupings. 5. The fibrillary plate lacks metachromasy, but shows a positive PAS-reaction. Before calcification a strong orthochromasy points to acid groups in connexion with the collagen. Under the radii there is no orthochromasy, and the PAS-reaction is negative. 6. When calcifying, the fibrillary plate loses its orthochromasy and the mineral matter is deposited as large crystal-complexes. 7. In regenerating scales the reactions are weaker than in normal scales.