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Updated: May 8, 2025
Thiersch contends that healing of a granulated surface results first from a conversion of the soft, vascular granulation-papillae, by contraction of some of their elements into young connective-tissue cells, into "dry, cicatricial papillae," actually approximating the surrounding tissues, thus diminishing the area to be covered by epidermis; and, secondly, by the covering of these papillae by epidermic cells.
In birds, however, the surface of the wing is supplied chiefly by feathers, and consideration of the matter affords no reason for supposing that the evolution of feathers was due to any external or functional stimulation. It is often stated that the feathers of birds are a modification of the epidermic scales of reptiles, but investigation does not fully confirm this statement.
It is covered with epidermic cells which multiply rapidly, thus accounting for the rapid growth of the hair. Around each papilla is a bulbous expansion, the hair bulb, from which the hair begins to grow. Epidermis of the Foot. It will be noticed that there are only a few orifices of the sweat glands in this region. The cells on the papillæ are the means by which the hairs grow.
It is a significant fact that even in man, according to the high authority of Virchow, the beautiful crystalline lens is formed in the embryo by an accumulation of epidermic cells, lying in a sack-like fold of the skin; and the vitreous body is formed from embryonic subcutaneous tissue.
The latter penetrates into the substance of the potato plant, either by entering a stomate, or by boring through the wall of an epidermic cell, and ramifies, as a mycelium, in the substance of the plant, destroying the tissues with which it comes in contact.
Ichthyosis is a disease of the skin characterized by a morbid development of the papillae and thickening of the epidermic lamellae; according as the skin is affected over a larger or smaller area, or only the epithelial lining of the follicles, it is known as ichthyosis diffusa, or ichthyosis follicularis.
Reverdin originated the procedure of epidermic grafting. Small grafts the size of a pin-head doing quite as well as large ones. Unfortunately but little diminution of the cicatricial contraction is effected by Reverdin's method.
Dermoid cysts of the ovary may consist only of a wall of connective tissue lined with epidermis and containing distinctly epidermic scales which, however, may be rolled up in firm masses of a more or less soapy consistency; this variety is called by Orth epidermoid cyst; or, according to Warren, a form of cyst made up of skin containing small and ill-defined papillae, but rich in hair follicles and sebaceous glands.
She inspects the peas, still on the vine, and enclosed in their pods; she auscultates them with her antennæ; she discovers, hidden under the general envelope, the weak points in the epidermic covering of the peas. Then, applying her oviscapt, she thrusts it through the side of the pod and perforates the circular trap-door.
Such epidermic anomalies as ichthyosis, scleroderma, and molluscum simplex, sometimes appearing shortly after birth, but generally seen later in life, will be spoken of in the chapter on Anomalous Skin Diseases. Human horns are anomalous outgrowths from the skin and are far more frequent than ordinarily supposed. Nearly all the older writers cite examples.
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