_The symptoms_ or lameness are more characteristic than in most diseases of the limb. At the very beginning of the inflammation, and sometimes for several months afterward, the lameness is intermittent and disappears with exercise. After a time it is permanent. It is characterized by a stiffness of the hock. The extension of the hock is incomplete, the step is short and quick, the animal "goes on its toe" and the wall or shoe at the toe shows considerable wear. Because of the stiffness in the hock the animal raises the quarter when the limb is carried forward. Turning toward the well side may increase the lameness. The _spavin test_ may be of value in diagnosing lameness. This consists in picking up the foot and holding the hock in a flexed position for a few minutes. The foot is then dropped to the ground and the animal moved off at a brisk trot. If the lameness is more marked, it indicates that the seat is in the region of the hock. This test is of greatest value in young animals. The bony enlargement can usually be seen best if the examiner stands in front and to one side of the animal. The hock should be observed from directly behind as well. The hocks of both limbs should be compared, and the general conformations of the other joints as well. This may prevent the examiner from mistaking rough hocks for spavin enlargements or "a pair" of spavins for rough hocks. A bony enlargement does not always accompany the lameness, and a spavin may be present without the horse going noticeably lame. [Illustration: FIG. 48.--Bog spavins.] _The prognosis_ is always uncertain and should be guided somewhat by the conformation of the limb, character of the work required of the animal, position of the bony enlargement and the degree of lameness. The size of the enlargement is changed very little by the treatment. Veterinarians report recoveries in from fifty to sixty per cent of the cases treated. _The object of the treatment_ is to destroy the inflammation and bring about a union between the bones. The treatment recommended is counterirritation and rest. The most satisfactory method of counterirritation is firing followed by blistering. Following this treatment, the horse should be placed in a stall and given no exercise for a period of five or six weeks. It is sometimes advisable to repeat the counterirritation if the results of the first firing are unsatisfactory. BOG SPAVIN.--Bog spavin is an extensive distention of the capular ligament of the hock-joint by synovia (Fig. 48). It is generally due to chronic inflammation of the synovial membrane. This blemish or unsoundness is most common in young horses. Thorough pin (Fig. 49) involves the sheath of the large tendon only. (Compare Figs. 48 and 49.) [Illustration: FIG. 49.--Thorough pin. Note the relation of the enlargement to the tendon, and the freedom of the hocks from bog spavin.]