Abstract
The electron histochemical properties characteristic of melanosomes as distinguished from mitochondria are presented. Our modified ammoniated silver nitrate reaction for electron microscopy reveals an essential chemical property of melanosomes which is also possessed by melanin granules, but is not possessed by any mitochondria. This property is the reduction of ammoniated silver nitrate to the metallic state.
Furthermore, melanosomes, and not mitochondria, are the only organelles which acquire the appearance of typically mature melanin granules after the electron microscopic dopa reaction.