The impregnating solution used in the technique shown in the image contains

• A. Silver protein
• B. Mercury chloride
• C. Copper sulfate
• D. Potassium dichromate

Answer: (A)

Silver impregnation relies on a silver-protein complex that serves as the carrier for silver ions. In this method, the tissue is exposed to a silver proteinate solution so the protein binds and carries silver into the specimen. When developed, the silver is reduced and deposited as metallic silver along the structures of interest, giving a sharp, dark outline of fine neuronal processes or reticular elements against a light background. This silver-protein impregnant is what makes the technique work, whereas the other reagents listed are used in different steps or methods and do not form the impregnant that directly enables the visualization of those structures.