The Skin Follicles

Each of the two molts in a year involves a series of changes in the shape and activity of the hair follicles in the skin (Figure 3.1). First, the follicles enlarge and extend themselves deeper into the skin. There they produce the new hair, which grows out alongside the old. If the growing hair is to be brown, the follicles contain a dark pigment, melanin. So in spring, the active growth of new brown hair can be detected from the small dark flecks on the inside of the skin, which represent the enlarged, active melanin-containing follicles.

Figure 3.1 The cycle of activity in the hair follicles of the skin during the molt and regrowth of brown hair. (a) Normal condition; (b) preparation stage; (c) growth of hair and follicle and accumulation of melanin; (d) formation of root; (e) shedding of old hair; (f) process complete, normal condition again.

Figure 3.1 The cycle of activity in the hair follicles of the skin during the molt and regrowth of brown hair. (a) Normal condition; (b) preparation stage; (c) growth of hair and follicle and accumulation of melanin; (d) formation of root; (e) shedding of old hair; (f) process complete, normal condition again.

By the time the new hair is fully formed and anchored in the follicle, the melanin is used up, and the follicle retreats back to its smaller resting state, nearer the surface of the skin. The inside of a dried skin now appears a clear, almost translucent honey color. The old hair is shed a few days, or even weeks, later. Hair cannot grow when the follicles are not active, and if a patch on the rump of a weasel is shaved during the resting phase, it will remain naked until the beginning of the next molt cycle (Feder 1990).

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