Golgi's stain

Any of several methods for staining nerve cells, nerve fibres, and neuroglia. In 1873 Golgi published a short note ('On the structure of the brain grey matter') in the Gazzetta Medica Italiana, in which he described that he could observe the elements of the nervous tissue "studying metallic impregnations... after a long series of attempts". This was the discovery of the 'black reaction' (reazione nera), based on nervous tissue hardening in potassium dichromate and impregnation with silver nitrate. Staining impregnates a limited number of neurons at random (for reasons that are still mysterious), and permitted for the first time a clear visualization of a nerve cell body with all its processes in its entirety.