168 THE VETERINARY DOCTOR. 
NAVICULAR DISEASE. 
The navicular bone is behind and below the lower bone of the pastern 
and above the coffin bone of the hoof. Diseases of this bone lead to many 
forms of obscure lameness. The bone may become contracted as a result, 
and this contraction has been erroneously considered by some the cause of 
the disease. The main causes are strain of the tendon that passes over the 
bone downward to the coffin, over-exertion, or long-continued work on 
hhard roads, by which the sac between the tendon and the bone becomes in- 
flamed and its oily fluid is stopped, leading to ulceration of the bone and 
membrane. 
Symptoms.—The horse stands with legs extended, putting the weight 
on the toe, the heel being lifted; perhaps the fetlock is bent, the toe thrown 
forward and stuck into the ground; !ameness; heat; tenderness of the foot; 
SECTION OF THE Foot AND PASTERNS. 
A, Coffin Bone. B, Navicular Bone, the seat of Navicular Disease. C, Coronary or Lower Pastern 
Bone. F, Cannon or Shank Bone. G, Horny Frog. H, Sensitive Frog. K, Sensitive Sole. L, Horny 
or Sensitive Sole. M, Outer Wall or Crust. N, Laminated Leaves or Horny Plates. O, Sensitive 
Lamina or Plates, the Chief Seat of Founder. 
lameness diminishes with exercise; pressure in the hollow of the pastern 
gives pain; tendon usually a little larger than is natural. After the dis- 
ease has run some time, pressure of the thumb on the hollow of the heel 
causes pain; the inside quarter of the foot becomes straighter, and ridges 
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