904 



NAVICULAR DISEASE. 



Acute inflammation of the navicular sheath is most commonly 

 the result of some mechanical injury to the foot, punctured wounds, 

 gathered nails, &c. In the case of gathered nail, the bursa is either 

 directly wounded, or infection extends to it from the sensitive frog. 

 Such acute conditions are described under " Diseases of the Hoof." 



In navicular disease the inflammatory process is aseptic, and 

 generally chronic, and the following structures are more or less 

 affected : navicular bone, navicular sheath, and perforans tendon. 



Fig. 516. — Preparation illustrating navicular disease. 1, Os pedis ; 2, flexor pedis 

 perforans tendon drawn downwards ; 3, lower (gliding) surface of the navicular 

 bone ; 4, coronet bone ; a and b, roughened, abraded spots on the flexor perforans 

 tendon ; c, eroded spots on the navicular bone ; d, proliferations from the upper 

 margin of the same bone. 



Pathology. Opinions are divided as to the point of origin of 

 the disease. Turner places it in the navicular bursa, and Fambach 

 considers the disease starts from rupture of tendon fasciculi. 

 Schrader and others locate the primary disease in the gliding surface 

 of the navicular bone. Brauell, however, maintains that the point 

 of origin is not constant, and that sometimes one, sometimes another 

 tissue first becomes affected. The fact that the perforans tendon is 

 nearly always found diseased does not prove that the first changes 

 occur in it, for immediately the surface of the navicular bone becomes 

 eroded or roughened the tendon is endangered. The gliding surface 



