C. Chemistry 66 D. Medicine 67 Theories of Metachromasy 68 A. Optical
Illusion 68 B Impurc Dyes 69 C. Dye Bases 69 D. Tautomers 70 E.
pH-Indicators 72 F. Colloidal Theories 72 G. Dimerization and
Polymerization 73 H. The Current Status ?4 Physiological Implications of
Chromotropes 76 A. Some Properties of Polyacidic Colloids 77 B.
Integrity of Connective Tissue 78 C. Blood Clotting 80 D. Cellular
Activation and Inhibitiou 81 E. Metaphosphate (Volutin) ..... 82 F. An
Evaluation of the Metachromatic Reaction 82 Acknowledgments 84
References 85 Introduction Metachromasy exists when a pure dye stains a
tissue section in a hue perceptibly different from the color characteri,
s.fically associated with the dye. Thus, a dilute solution of toluidine
blue i8 blue. Cell nudei and certain basophilic components of the
cytoplasm are stained in this color. A number of other histological
elements are stained red by toluidine blue. The laNer is the
metachromatic color of the dye. Both extremes of color, as well as
intermediate hues, may prevail in the same histological pre- paration.