Exostoses are somewhat uncommon in the bovine species, and when they occur are rarely of great clinical interest. Nevertheless, in cows and old working oxen one sometimes sees metatarsal spavin. Its gravity, however, appears to be very much less than in the horse, on account of its position. Very commonly there is only trifling lameness. Treatment by application of biniodide of mercury ointment or the actual cautery gives good results. The principal precaution required is to prevent the animals licking the parts. RING-BONE. Ring-bones only occur in working oxen, and particularly in aged animals used in hilly regions. They result almost exclusively from wounds, ligamentous and tendinous strains, and articular injuries. [Illustration: $1] They are preceded (as can usually be proved by dissection of limbs) by fibrous or fibro-cartilaginous induration in or about the coronet or one of the phalanges. These thickenings increase the diameter of the pastern in all directions. Ring-bones are seldom very large; but as they partially or entirely surround the insertions of the lateral ligaments, inter-phalangeal articulations or insertions of the digital extensors, they are painful, and produce lameness of varying intensity. =Diagnosis= is easy, partly because the tension of the skin and the fibrous thickening render palpation painful. =Prognosis= is grave, because the effect of ring-bone is sometimes to render working animals useless. [Illustration: $1] [Illustration: $1] =Treatment.= To relieve the diseased claw of pressure due to its bearing on the ground, the shoe should be removed and the claw freely pared. If necessary, the healthy claw of the same foot may be raised by placing a piece of thick leather between the sole and the shoe. It is advisable at once to apply an energetic plaster, or, better still, to resort to firing in points. SUPPURATING OSTITIS. In addition to the changes in bone resulting from rachitis, osseous cachexia, tuberculosis, and actinomycosis, one sometimes sees cases of periostitis or ostitis pure and simple. As a result of external injury or direct wounds, the bone may be contused and injured, becoming the seat of diffused periostitis, necrosis, suppurating ostitis or osteomyelitis. Open fractures may produce the same results. =Treatment= comprises disinfection of wounds, antiseptic injection of fistulæ, the application of antiseptic pencils, curettage, the removal of sequestra, and vesicant or resolvent complications. When such conditions extend to neighbouring joints and produce suppurative arthritis, the animals ought to be killed. BONE TUMOURS. The only bone tumours of real importance from a practical point of view are malignant growths represented by rapidly spreading epitheliomata or sarcomata, originating in the periosteum. Fortunately such tumours are rare.