These are arranged in distinctive, often overlapping patterns. Beneath the cuticular scales is the cortex , an often-thick layer that appears featureless except that it may be pigmented. At the center of most hairs is the medulla , made up of large, cuboidal cells, often distinctively colored and interspersed with air pockets. The arrangement of scales, thickness and color of the cortex, and distribution and color of medulla cells are often diagnostic of species. Using a microscope, a researcher can easily examine the cortex and medulla of individual hairs.
Hairs also differ in cross-sectional shape.
The color of hair is due to a group of proteins called melanins . Eumelanin is very dark, pheomelanin is paler. The pelage of most mammals consists of more than one kind of hair. The most conspicuous hairs on most mammals are the guard hairs , which overlay the fur and serve to protect it. An especially important class of hairs is the vibrissae or whiskers .