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;.
Warts are small, rough, scaly tumors or abnormal growths formed by a thickening of the skin; they may come on any part of the body or limbs, but are often seen in great numbers about the nose and eyelids. If they are very small and numerous, as is often the case about the nose, they can often be removed by a daily application of castor oil with plenty of hand-rubbing. But if they grow singly the best plan is to take a sharp knife and cut them out, including a narrow strip of healthy skin all around the wart to insure getting all the roots. Flat warts may sometimes be removed by touching once a day with nitric acid, but do not let it get on the healthy skin.
There is a species of tumor commonly called "bleeding wart" that grows on the lower or less fleshy part of the leg of the horse as the result of some deep-seated injury, frequently from a neglected wire cut where the covering (periosteum) of the bone has been injured. If not taken in its early stages it is very difficult to control, as cutting out, unless every particle is removed, only seems to make it grow more rapidly.
Treatment. - Remove the tumor with a knife to the level of the skin, then make enough paste to cover the tumor, as follows: Take chloride of zinc, and just enough water to dissolve it; add enough wheat flour to form a paste; spread this over the surface of the tumor; lay on a piece of cotton to keep it from spreading and apply a bandage around the whole for twenty-four hours, then remove it. Keep the part oiled and in a week or less the dead tissue will drop out, when, if any of the roots remain, the process should be repeated. When it is all out the wound can be healed by a daily application of the following wash: Chloride of zinc, three drachms; rain water, one pint; mix.
Melanosis is a disease peculiar to white or gray horses; sometimes, though not often, seen in others. It manifests itself in black, hairless tumors resembling rubber. They may occur on any part of the body, but are oftenest seen about the root of the tail and around the anus. If small they may be dissected out; if large, and deep in the muscles, let them alone.