Protargol demonstrates which tissue component?

• A. Nerve fibers
• B. Myelin
• C. Axons
• D. Glial cells

Answer: (A)

Protargol is a silver-based impregnation stain used to visualize the fibrous components of nervous tissue. It deposits silver in the neurofilaments and related cytoskeletal elements within nerve fibers, so the axons and their extensions appear as dark, well-defined structures against the surrounding tissue. This makes the network of nerve fibers stand out, which is why Protargol is described as demonstrating nerve fibers. It does not specifically highlight myelin sheaths, which are best seen with stains like Luxol fast blue or osmium tetroxide, nor does it selectively label glial cells. Axons are part of nerve fibers, so Protargol visually reveals them as part of the nerve fiber tract.