Fig. [73]. Corn.
Fig. [74]. Wart.
A Wart (fig. 74) depends chiefly on a diseased state of the papillary stratum of the skin. The papillæ become coarse and grow up beyond the level of the surrounding skin, so as to present an uneven or “warty” surface. They carry a layer of cuticle before them. This layer is usually thin, so that the wart bleeds easily when it is rubbed. Sometimes, however, it is very thick and hard like a piece of horn. We, now and then, hear of a horn growing upon some part of the body, perhaps on the forehead. Such a horn is, usually, nothing more than a conical mass of cuticle formed upon the surface of a large wart. Warts are generally caused by something irritating the skin, as dirt or soot rubbed into the cuticle. For this reason they are more frequent upon the hands than upon other parts of the body.
In a Corn (fig. 73), also, the papillæ are somewhat enlarged; and this accounts in part for the great tenderness of corns. But the primary and essential feature of a corn is a thickened state of the cuticle. This is caused by too great rapidity in its formation, and is, usually, dependent upon pressure, especially if the pressure be combined with some friction. Hence corns are most commonly found upon the foot, and upon the parts of the foot, where the skin is subject to pressure and rubbing against the shoe. The drawing shows the appearance presented by a vertical section through a corn and through a small portion of the skin on either side. The accumulated layers of cuticle are seen, and the enlarged papillæ shooting up into them. I need scarcely add that it is owing to ignorance, or something worse, when corn-cutters talk of curing the malady by taking out the roots; for, corns, evidently, have no roots.
One word of advice about corn-cutting. Most persons have some experience in this art, and some opportunity of practising it on themselves; and many pride themselves on their skill in it. The usual plan is to shave off layer after layer from the whole surface of the corn; and this, by lessening the projection of the corn, may give relief for a few days, though it does not always do that. Soon, however, the distress returns; and the area of the corn increases after each operation. Now, I would have you observe that it is at the middle of the corn that the papillæ are most enlarged; and it is here that the formation of cuticle goes on most quickly, giving rise to the little white cone or cones often seen in a corn and sometimes wrongly called the roots. The proper mode is to confine the cutting to this part, and to remove as much of the thickened cuticle as you can from this spot, digging, as it were, a hole in the middle and leaving the circumference intact. The circumference, which is not usually tender, thus forms a wall round the excavated centre and defends it from pressure; and great relief is experienced. Further benefit will be found from covering the corn with some soft adhesive plaster; and you may sometimes, with advantage, lightly apply common caustic before putting on the plaster. If you follow these directions carefully you may be your own chiropodists, and almost defy your bootmakers.
If, in cutting a corn, you go too deeply, you will wound the tops of the papillæ and cause some bleeding; this is not however usually followed by any ill consequences.
Nails.
Almost all vegetable as well as animal surfaces are covered with some kind of cuticle. It forms the smooth exterior of a leaf and the rind of an apple; and the soft down of a moth or a butterfly, the scales of fish, the feathers and claws of birds, the quills of the porcupine, the horns of oxen and the hoofs of the horse are examples of modifications of cuticle. NAILS and HAIR are also of this nature. They are both continuous with the cuticle, and peel off with it when it is, by any process, separated from the skin. Both are formed, like the cuticle, of compressed plates or scales matted together; and these are continually being shed or rubbed off on the one side, and supplied from the rete mucosum on the other.