| | 2. Salt Rheum. |_7. DISEASES. | 3. Corns. | 4. Ingrowing Nails. | 5. Warts. |_6. Chilblains. THE SKIN. THE SKIN is a tough, thin, close-fitting garment for the protection of the tender flesh. Its perfect elasticity beautifully adapts it to every motion of the body. We shall learn hereafter that it is more than a mere covering, being an active organ, which does its part in the work of keeping in order the house in which we live. It oils itself to preserve its smoothness and delicacy, replaces itself as fast as it wears out, and is at once the perfection of use and beauty. 1. STRUCTURE OF THE SKIN. CUTIS AND CUTICLE.--What we commonly call the skin--viz., the part raised by a blister--is only the cuticle [Footnote: _Cuticula_, little skin. It is often styled the scarfskin, and also the epidermis (_epi_, upon; and _derma_, skin).] or covering of the cutis or true skin. The latter is full of nerves and blood vessels, while the former neither bleeds [Footnote: We notice this in shaving; for if a razor goes below the cuticle, it is followed by pain and blood. So insensible is this outer layer that we can run a pin through the thick mass at the roots of the nails without discomfort.] nor gives rise to pain, neither suffers from heat nor feels the cold. The cuticle is composed of small, flat cells or scales. These are constantly shed from the surface in the form of scurf, dandruff, etc., but are as constantly renewed from the cutis [Footnote: We see how rapidly this change goes on by noticing how soon a stain of any kind disappears from the skin. A snake throws off its cuticle entire, and at regular intervals.] below. Under the microscope, we can see the round cells of the cuticle, and how they are flattened and hardened as they are forced to the surface. The immense number of these cells surpasses comprehension. In one square inch of the cuticle, counting only those in a single layer, there are over a billion horny scales, each complete in itself.--HARTING. FIG. 22. [Illustration: A _represents a vertical section of the Cuticle._ B, _lateral view of the cells._ C, _flat side of scales like_ d, _magnified 250 diameters, showing the nucleated cells transformed into broad scales._]