Corns (Lat. cornu, 'horn,' through the French) are small hard growths, resulting from an increase in the thickness of the cuticle or epidermis, which is generally caused by the irritation of some excessive pressure or friction on the part. They occur most commonly on the feet as a result of tight or ill-fitting shoes. Corns are either hard or soft; the structure of both classes is essentially the same. A hard corn begins as an ill-defined thickening of the epidermis at one point. As irritation continues, the excessive growth of epidermis increases, and the papillæ (see SKIN) beneath also enlarge, giving the deeper part of the growth a fibrous appearance, popularly described as the 'roots' of the corn. Pressure upon the sensitive nerves of these papillæ causes the usual pain of corns. Old corns often have a bursa or sac developed beneath them, which in part protects the underlying structures. Excessive irritation sometimes causes this bursa, or in its absence the connective tissue beneath a corn, to inflame and suppurate; and the little abscess thus formed, confined by the hardened epidermis, gives rise to intense suffering. In so-called fibrous corns, more allied to warts, the enlargement of the papillæ predominates, and the pain is greater than in ordinary hard corns. Soft corns occur between the toes, where the warmth and moisture promote early separation of the epidermis, and growth of the papillæ; they are therefore more vascular than the other forms, and often extremely painful.
The treatment of corns consists in the removal of all undue pressure or friction, either by removing the shoe altogether, or protecting the corn by surrounding it with a border of some soft material, as Amadou (q.v.) or soft leather; or the hardened cuticle may be pared or filed away, the central part most deeply. Of late years a simple and convenient remedy has been introduced, now sold everywhere as a 'certain and painless cure for corns.' It consists of a solution of salicylic acid in collodion, one drachm to one ounce, with a small proportion of extract of Indian hemp. It is painted over the corn once or twice daily, and allowed to dry, with the effect of so softening the epidermis that, usually after six or eight applications, it can readily be peeled off with the aid of hot water. Soft corns should be freely dusted with oxide of zinc powder, and the affected toe isolated from its neighbours by means of medicated cotton-wool. If suppuration occur beneath a corn, the matter must be let out by a puncture, after the corn has been pared down. Those subject to corns should avoid patent leather boots, or even eschew leather altogether, and use 'pannuscorium' or some other more porous substitute.
Corns affect horses as well as men. In the foot of the horse they occur in the angle between the bars and outer crust, and consist in a bruise of the sensitive secreting sole. Some forms of feet are especially subject to them. Corns constitute unsoundness; cause a short, careful, tripping gait; are the most frequent source of lameness amongst roadsters; abound in badly-shod horses, and usually occur in the inside heels of the fore-feet, these being more especially subjected to weight, and hence to pressure. The discoloured spot indicating the recent corn must be carefully cut into with a fine drawing-knife; any serum or blood is thus allowed free vent. If the bruise has been extensive, a poultice will have the twofold effect of allaying irritation and relieving the sensitive parts by softening the hard unyielding horn. When the injury has been of some standing, and soft faulty horn is secreted, a drop of diluted nitric acid may be applied. On no account must the bars or outer crust be removed; they are required for bearing weight, which may be further kept off the injured part by the use of a bar-shoe. In horses subject to corns, harden the feet by putting on tips or slippers instead of full shoes, thus bringing the heels into contact with the ground; this will cause a rapid and strong growth of horn, not liable to be bruised.