242 VETERINAKY MEDICINE AND SUEGERY. 



Nitrate of potassium 3 ij. 



In water twice daily. 



will probably be beneficial in the first instance, followed after a time by 

 tonics, as sulphate of iron or quinine. Good dry food, fresh air, great 

 cleanliness, and a dry stable and bedding are essential. 



NAVICULAR DISEASE. 



Synonym. — Navicular arthritis. 



Definition. — Navicular disease, in its primary stage, is inflammation 

 of the lower side of the navicular bone. After a time the neighboring 

 parts, viz., the perforans tendon which passes under the bone, and its 

 cartilage and bursa become involved. 



Etiology. — Navicular disease is commonly due to the effect of con- 

 cussion; more rarely to nails, stones, etc., picked up by the foot. 



It will be remembered that the navicular bone acts as a roller for the 

 passage of the perforans tendon, which passes under it and is attached 

 to the coflSn bone. Hence the navicular bone is peculiarly liable to suf- 

 fer from the effect of concussion. 



Navicular disease occurs most frequently in feet with narrow and 

 high heel. It rarely affects the hind feet. 



The primary disease is inflammation of the navicular bone. The 

 parts subsequently involved are the cartilage covering its inferior surface, 

 the synovial membrane, the bursa of the tendon (flexor pedis perforans) 

 passing under the bone, and ultimately the tendon itself. This tendon 

 passes under the bone, as a rope under a pulley. 



The inflammation which has been set up in the bone, leads to u vari- 

 ety of changes, both in its external and internal structure. In some 

 cases the bone gradually wastes away until at last it becomes liable to 

 fracture from any trivial cause. In other cases, an ossific deposit takes 

 place upon the outside of the bone. This deposit limits the free play of 

 the tendon, which gradually adheres to the bone, and its bursa becomes 

 absorbed. In other cases, the fibres of the tendon split up, sometimes 

 from friction against the roughened surface of the diseased bone, but 

 n^.ore frequently as the result of degeneration caused by inflammatory 



