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THE HORSE’S FOOT. 
467 
sheath .between the navicular bone and the perforans tendon, slid¬ 
ing upon it. At first may be observed a certain injection of the 
synovia, and a darker hue in the coloration of the trochlear car¬ 
tilage with the corresponding face of the tendon, the synovia be¬ 
coming reddish and thick, the surrounding cellular tissue becom¬ 
ing, also, inflamed and infiltrated. At a later period, when the 
disease has somewhat progressed, there is a thickening of the 
walls of the capsule, which is then filled with a clear citrine serosity. 
There is then, a kind of hygroma, a chronic dropsical condition 
of the sheath. In the interior of this are found fibrous bands, 
running from the tendon to the bone. If the disease is older, 
erosions are found upon the diarthrodial surface of the navicular, 
varying in number and in size, and the tendon is roughened on its 
anterior face, with longitudinal fissures. At times, it becomes 
atrophied and thin, dry and brittle; and has been found,it is said, 
ruptured transversely. In many cases, the cartilage covering the 
bone has disappeared and the bone is exposed, hollowed and 
affected with osteoporosis. The union of the bone with the ten¬ 
don has also been found among the varieties of determination. 
IV. — Diagnosis .—This disease is at first easily mistaken for 
some form of rheumatic affection. Where pain is the main symp¬ 
tom it is easily detected, but where there are no other signs of 
inflammation, it is just the lack of proportion between the inten¬ 
sity of the lameness and the serious symptoms, such as the absence 
of heat; of special sensibility ; of pulsations in the digits, which 
distinguishes navicular disease from other affections of the feet. 
The error with contracted heels is easier, as here the change of 
form of the foot being primitive, at once attracts the attention 
of the practitioner ; while this alteration in the foot is absent in 
navicularthritis at the outset of the disease. 
V. — Prognosis. —Generally, it is unfavorable, as most com¬ 
monly the veterinarian is called only when the disease has already 
made serious progress and passed into the chronic stage ; and 
again, because of the difficulty of reaching the disease by reason 
of its peculiar location. 
(To be continued .) 
