NAVICULAR DISEASE. 
639 
In rare cases the disease occurs metastaticallv after influenza, and 
then generally in badly-bred and flat-soled horses, a fact which perhaps 
explains Brauell’s statement that horses often suffer from the disease 
after having had diarrhoea. This was possibly due to secretory metastasis, 
disease of the bursa occurring in consequence of specific micro-organisms 
obtaining access to it. 
Symptoms and course. The more important symptoms are— 
(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. 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. As pressure on the affected navicular bone 
is greatest when the limb is directed backwards, 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 bone 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, depend¬ 
ing on the position, nature, and extent of the disease. It is usually 
more marked after great exertion. It occasionally disappears com¬ 
pletely after a long rest—a fact which renders diagnosis difficult, and 
may give the impression of recovery. To sum up, the symptoms are 
as follows:—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 
