As each hair shaft grows out of its hair follicle, these plate-like structures are laid down on the outer cortex of the shaft in particular patterns. Among the wonders found in this book are microphotographs of a variety of tying materials that aid greatly in understanding why they do what they do. Note pages 75 and 76 where the scales on beaver and whitetail deer are shown. The difference between the two animal's scales is impressive.
Beaver hair has somewhat random plates wrapped about the shaft.
Deer hair scales look like fish scales, and lay on the hair from root end to tip essentially as a fish's scales lay on it from head to tail. It is thought that perhaps the scales help to protect the skin from foreign matter. Since scales bevel away from the hair shaft in a direction toward the tip, this arrangement would hinder dirt from working down toward the skin. For dirt that did manage to get down to the skin, the scales would help to migrate it toward the hair tips and off of the animal. Scanning electron micrograph of a hair showing the scales.