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;.
Canker is an obstinate disease which may follow a neglected case of any of the diseases in which the sole or wall becomes broken or destroyed, and the sensitive parts become involved. Filth also is a very active factor in producing it. It sometimes starts from grease heel.
Symptoms - A spongy, fungus growth springs up from some old wound about the foot, making the horse lame. It is hard to control and if cut away soon grows out again. It sometimes grows up in leaves or flakes and bleeds very easily.
Treatment. - Cut away all that can be reached with the knife and control the bleeding by searing with a hot iron or by applying tincture of iron and binding it up in cotton till next day. When all bleeding has been stopped take chloride of zinc and add just enough water to dissolve it; apply it freely, and saturate cotton with the zinc solution and bind on the part, keeping it there for twenty-four hours. When the fungus growth has been completely destroyed, dust the sore once a day with calomel and cover with cotton saturated with pine tar and apply pressure. If the fungus growth begins to start up again dust it over with powdered blue vitriol. If you are persevering you may succeed in curing it, but it will take time.