The keratin in the epidermis, when thickened and cornified, is referred to as [[Horn - Anatomy & Physiology|horn]]. Horn is particularly resistant to mechanical and chemical damage. The outer surface of the hoof is composed of horn. | The keratin in the epidermis, when thickened and cornified, is referred to as [[Horn - Anatomy & Physiology|horn]]. Horn is particularly resistant to mechanical and chemical damage. The outer surface of the hoof is composed of horn. |