Spinal cord white matter, stained with Luxol Blue. In routine stains, such as Luxol Blue, only the nuclei of gliocytes can be seen. Typical astrocyte nuclei (astr) are relatively large, oval, and chromatically stippled. Typical oligodendrocyte nuclei (oligo) are small, round, and packychromatic. Myelinated axons (a) are evident within vacuoles (m) artifactually produced by lipid extraction from myelin during tissue processing. The resultant blue-stained protein residue of myelin is called neurokeratin.