Volume 2

Health lectures for the people.

Date:
1883-1892
Catalogue details

Licence: Public Domain Mark

Credit: Health lectures for the people. Source: Wellcome Collection.

    106/600 (page 94)
    the skin rests. Unlike the epidermis, the true-skin is plentifully supplied with blood-vessels. Both layers of the skin take part in the formation of the hair- follicle. It is, as it were, a narrow tubular depression of the skin which has carried both epidermis and corium before it (Fig. 1). The wall of the hair-follicle has therefore two distinct layers entering into its formation—the inner layer being cellular and epidermic, whilst the outer layer is fibrous and continuous with the corium. When a hair is plucked from the skin the inner layer of the follicle adheres to the root, and is in great part with- drawn with it. It is therefore termed the root-sheath. But you ask, what is the depth of a hair-follicle, and is it equally deep in every case ? It varies very greatly in this respect. Those which hold the short hairs do not sink beyond the skin. The follicles of the larger hairs of the scalp and beard on the other hand are much longer, and penetrate beyond the skin into the subcutaneous fatty tissue. Another point to be noticed in connection with the hair follicle is this : that, with the exception of those which contain the eyelashes, they are seldom perpen- dicular to the surface. They have a slanting or oblique direction. Let us now enquire into the manner in which a hair is fixed in its follicle. If you examine a fresh hair-root, you will notice that its extremity is expanded into a knob which we term the hair-bulb. This hair-bulb is composed of cells like those of the root-sheath, and at the bottom of the follicle the two are directly continuous with each other around the circum- ference of the bulb. Again, at the bottom of the hair-follicle there is a little fungiform projection continuous with the fibrous corium. It is called the hair-papilla, and contains both blood- vessels and nerves (Fig. 1). As we shall afterwards see this papilla is of the utmost importance in connection with the process of hair growth. It is also an agent, however, in fixing the hair in its follicle. The lower aspect of the hair-bulb is hollowed out into a cavity, and the papilla is received into this in the same manner that a head is received into a cap (Fig. 1). If you have followed what I have said, you will see that the