myelin

1. (neuroanatomy) A white, fatty material, composed of lipids and lipoproteins, that surrounds the axons of nerves.Examples: "As the result of prolonged action of water upon myelin, bird's-nests-cells are also said to be produced, and we are certain we have seen, as the result of such prolonged action of water, the appearances thus compared."; "This gene controls the production of an insulating sleeve that wraps around neurons. Known as myelin, it is crucial for long-range communication in the brain."countableuncountable