Myelin sheath (Myelin Sheath) is a membrane wrapped around the outside of the axon of a nerve cell, i.e., myelin sheath consists of myelin cells and cell membranes, and it is a multilayered lipid bilayer structure formed by the plasma membrane of the nerve membrane cells spirally winding along the axis of the axon, and there is a Langfei's knot on the myelin sheath, which can enable the nerve impulses to jump to be transmitted, and the staining of myelin sheaths is of some significance in the pathology of diagnosis, and the pathology of myelin sheaths is divided into the early, intermediate, and The pathological changes of myelin sheath are divided 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 changes in myelin, Weil myelin staining can show whether the myelin sheath is intact, degeneration, degree of necrosis and repair in pathological conditions, which is meaningful for the pathological diagnosis and study of nerve tissue, for example, when nerve fibers are damaged, the myelin sheath can appear to be swollen, zigzagged into a spherical shape, fracture, or desheathing completely disappeared and other changes.

Weil iron alum hematoxylin staining solution, also known as Weil hematoxylin staining solution, is mainly composed of hematoxylin, iron alum, ethanol, etc. It is mixed before use and used for staining paraffin sections of myelin sheath.