The cells are very distinct, with nuclei enclosing pigmentary granulations (Magnified 350 times)]

A, membrane of the hair-follicle, cells with nuclei and pigmentary granules; B, external lining of the root sheath; C, internal lining of the root sheath; D, cortical or fibrous portion of the hair shaft; E, medullary portion (pith) of shaft; F, hair-bulb, showing its development from cells from A. ]

They are usually set down as due to varying degrees of oxidation in the pigmentary matter.