SYMPTOMS OF NAVICULAR DISEASE. 909 



Symptoms and course. (1) Lameness. On account of its slow 

 development the beginning of the disease is generally overlooked, 

 and attention only directed to the parts after pain and lameness 

 are present. Many cases are ushered in by slight unaccountable 

 lameness or by loss of action, which is often best marked in trotting 

 downhill. Lameness begins gradually : the first few steps, 

 particularly if taken on hard ground, are painful, but this often 

 disappears completely with exercise. When both feet are affected 

 diagnosis is still more difficult. There may only be a tendency to 

 stumble (Smith). The seat of disease explains why pain should be 

 most marked when weight is placed on the limb. Even in the stable 

 the diseased foot is rested — the horse pointing. As pressure on the 

 affected navicular bone is greatest when the limb is directed back- 

 wards, at which time, of course, the flexor perforans is in greatest 

 tension, the animal endeavours, as far as possible, to shorten this 

 phase of movement, and, to remove weight from the tendon, the 

 foot is held in a position of volar flexion with the pastern bones 

 upright, sometimes to such a degree that the heels scarcely touch 

 the ground. The gait then becomes stiff and insecure, and the animals 

 readily stumble. When both feet are diseased the animal tries to 

 shorten those phases of movement in which weight is borne 

 exclusively by one foot, and the limb is therefore carried stiffly and 

 rapidly forwards. Spooner says the animal moves as though it 

 had a wooden leg. Owing to the pain the horse moves slowly, 

 sweats, and soon becomes exhausted. 



Sometimes the difficulty in movement disappears after a few 

 steps : sometimes it is permanent, or may even increase with exercise, 

 depending on the position, nature, and extent of the disease. It 

 is usually more marked after a short rest following great exertion. 

 It occasionally disappears completely after a long rest — a fact which 

 renders diagnosis difficult, and may give the impression of recovery. 

 To sum up, lameness when weight is placed on the limb, increased 

 after considerable exertion, decreased by long rest ; volar flexion 

 of the phalanges and extension of the foot, particularly during the 

 first few steps. 



(2) Changes in the hoof. The local inflammation may be detected 

 by exercising pressure on the navicular bone. One jaw of the pincers 

 is applied over the centre of the frog, the other over the wall of the 

 toe. Hertwig's special pincers are unnecessary ; but if the sole 

 and bars are very thick, they should be thoroughly pared before using 

 the pincers. Pain can sometimes be detected by pressing with the 

 thumb in the hollow of the heel. In doubtful cases Brauell 



