This section is from the book "The Farmers Ready Reference Or Hand Book Of Diseases Of Horses And Cattle", by S. C. Orr. . Also available from Amazon: The Farmer's Ready Reference;.
Corns are bruises of the sensitive part of the sole of the foot in the angle formed by the junction of the bar and the wall. They are the result of undue pressure from the shoe, sometimes caused by improper shoeing, but. just as often caused by leaving the shoe on the foot too long, with a mistaken idea of saving expenses.
Symptoms. - Lameness, especially on hard ground; the horse will point the foot when standing. Take up the foot and tap it with a hammer or try it all around with a pair of pinchers and the horse will show signs of pain when you touch the tender spot. If you remove the shoe and clean out the angles, the bottom of the hoof in the angle is generally tinged with blood.
Treatment. - Remove the shoe and dress down the heel; clean out the angles and cut down carefully; if there is pus, cut away enough of the sole to give it free exit. But if it is dry, do not cut to the quick, but only thin it down. Cut away the wall slightly to let the frog down on the ground. If pus has formed, after evacuating it hold the foot up and fill the angle full of muriatic acid or muriate of antimony. Apply a warm linseed-meal poultice every day till the tenderness is removed, then fill the angle with cotton saturated with pine tar to keep out foreign matter; the tar is also beneficial to the foot. After the sole at the seat of the corn has become somewhat hardened the shoe may be replaced, but the foot should be so dressed as to relieve the corn of all pressure, or it will return again. Horses that are subject to corns will be greatly benefitted by allowing them to go without shoes as much as possible, and even then the heels should be dressed down occasionally to let the frog upon the ground, and the angles should also be cleaned out.