Ceratin

noun

1. The proper substance of horn or horny tissue; the organic substance of the ceratina, entering largely into the composition of epithelial or cuticular structures, as horns, hoofs, nails, etc. Also keratin, keratine.
2. a fibrous scleroprotein that occurs in the outer layer of the skin and in horny tissues such as hair, feathers, nails, and hooves