Other glands terminate under the skin in the hair
follicles, which follicles or hair sockets contain or enclose the hair
roots. These glands terminating in the hair follicles secrete an oily
substance, which bathes and lubricates as well as nourishes the hair.
With respect to the origin of the hair or wool fibre, this is formed
inside the follicle by the exuding therefrom of a plastic liquid or
lymph; this latter gradually becomes granular, and is then formed into
cells, which, as the growth proceeds, are elongated into fibres, which
form the central portion of the hair. Just as with the trunk of a tree,
we have an outer dense portion, the bark, an inner less dense and more
cellular layer, and an inmost portion which is most cellular and
porous; so with a hair, the central portion is loose and porous, the
outer more and more dense. On glancing at the figure (Fig. 6) of the
longitudinal section of a human hair, we see first the outer portion,
like the bark of a tree, consisting of a dense sheath of flattened
scales, then comes an inner lining of closely-packed fibrous cells, and
frequently an inner well-marked central bundle of larger and rounder
cells, forming a medullary axis.
Pages:
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28