What reagents are contained in the Weil staining solution?

• A. Hematoxylin, ferric ammonium sulfate
• B. Cresyl echt violet, Crystal violet
• C. Phosphotungstic acid-hematoxylin, Gold sublimate
• D. Hematoxylin, Luxol fast blue

Answer: (A)

Weil staining is used to demonstrate myelin and relies on an iron-hematoxylin system. The key is hematoxylin combined with ferric ammonium sulfate acting as the mordant. The ferric ions form a hematoxylin-iron complex that binds strongly to the lipid-rich myelin in nerve fibers, producing a dark blue-black stain. Therefore, the reagents in Weil staining solution are hematoxylin and ferric ammonium sulfate.

The other pairs correspond to different stains: Cresyl echt violet with crystal violet are alternative basic dyes used in other contexts; phosphotungstic acid-hematoxylin with gold chloride is PTAH staining for muscle and nerve components; hematoxylin with Luxol fast blue is a Luxol fast blue protocol for myelin but not Weil.