Mammalian hair is composed of a protein, keratin. It is the same protein that makes horn, fingernails, claws, skin epithelium, and dander. Mammalian hair consists of three distinct morphological units, the cuticle, the cortex and the medulla. In addition to these units pigment bodies and other inclusions can help distinguish one hair type from another. A brief illustrated glossary of terms is presented below to aid in the interpretation of structure accompanying the individual photographs. These terms are largely taken from L. A. Hausman