Myelin sheath (Myelin Sheath) is a membrane wrapped around the axon of nerve cells, that is, myelin sheath consists of myelin cells and cell membranes, is the plasma membrane of the nerve membrane cells along the axis of the axon of the helical winding formation of multilayered lipid bilayer structure, myelin sheath on the Langfei's node, which can make nerve impulses jumping transmission, myelin sheath staining in the pathologic diagnosis of a certain significance, myelin sheath pathological changes are divided into the early, intermediate and The pathological changes of myelin are categorized into early, middle and late stages. In the early stage, the coloring is darker; in the middle stage of the lesion, myelin degenerates to form lipid droplets, which can be shown by lipid staining, and in the late stage, it completely collapses and is cleared by phagocytes, so there is no longer a positive result for myelin.

Many diseases can cause myelin changes, Weil myelin staining can show whether the myelin sheath is intact, degeneration, the degree of necrosis and repair under pathological conditions, which is meaningful to the pathological diagnosis and study of nerve tissue, for example, when the nerve fiber is damaged, the myelin sheath can be swollen, zigzagged into a spherical shape, fracture, or complete loss of desheathing and other changes.