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The hair and the nails are important modifications of the epidermis. *A Hair* is a slender cylinder, formed by the union of epidermal cells, which grows from a kind of pit in the dermis, called the hair follicle. The oval and somewhat enlarged part of the hair within the follicle is called the root, or bulb, and the uniform cylinder beyond the follicle is called the shaft.
On turning from foliar expansions, to stems and roots, facts of like meaning meet us. Speaking generally of epidermal tissue and inner tissue, Sachs remarks that "the contrast of the two is the plainer the more the part of the plant concerned is exposed to air and light."
On this epidermal bag, this sort of transparent leather bottle, formed by the larva's skin detached all of a piece, without a slit of any kind, we can distinguish the several well-preserved external organs: the head, with its antennæ, mandibles, paws and palpi; the thoracic segments, with their vestiges of legs; the abdomen, with its chain of breathing-holes still connected one to another by tracheal threads.
Material for the growth of the nail is derived from the matrix, which is lined with active epidermal cells and is richly supplied with blood vessels. The cuticle adheres to the nail around its entire circumference so that the covering over the dermis is complete. *Functions of the Skin.*—The chief function of the skin is that of protection.
The principal epidermal characteristic of a true wool is the capacity of its fibres to felt or mat together. Just as with hair, the scales of which have their free edges pointing upwards away from the root, and towards the extremity of the hair, so with wool.
Not even savages hesitate to defer in all their important designs to the sought-for guidance of superior judgments. But in the case of us West Indian Blacks, to whom Mr. Froude's doctrine here has a special reference, is it suggested by him that the bidders for predominance over us on the purely epidermal, the white skin, ground, are ipso facto the monopolists of directing wisdom?
The new one just received from Australia, which I am now about to describe, in this respect more resembles the Margarita than any before noticed; yet I am inclined to think that the pearl-shells deserved to be kept separate, as the cardinal teeth are quite obliterated in the adult shells, which is not the case with any AVICULAE I am acquainted with; and the young pearl-shells are furnished with a broad serrated distant leafy fringe, while the AVICULAE are only covered with very closely applied short concentric slightly raised minutely denticulated lamina, forming an epidermal coat on the surface.
In the higher Algæ "the outermost layers consist of smaller and firmer cells, while the inner cells are often very large, and sometimes extremely long;" and in the leaves of trees the epidermal layer, besides differing in the sizes and shapes of its component cells from the parenchyma forming the inner substance of the leaf, is itself differentiated by having a continuous cuticle, and by having the outer walls of its cells unlike the inner walls.
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