20G 



THE DISEASES OF THE HORSE. 



NAVICULAR DISEASE (Grogginess), 



Is a rarifying inflammation of the navicular bone, with 

 death of the articular cartilages and surrounding structures. 

 The tendon of the flexor pedis perforans muscle is subse- 

 quently inflamed and becomes adherent to the navicular 

 bone. Concussion and rheumatic predisposition are be- 

 lieved to be the chief causes. (Dun.) 



It is the most fertile cause of lameness, and is the bane 

 of horse flesh. Strain or laceration of the tendon is never 

 a primary condition. The disease begins as an inflamma- 



Fig. 91 represents the phalangeal bones in their naturally oblique position. 

 The upper part of the long pastern bone (a), to toe of os pedis (c), is a 

 continuously oblique line. This obliquity of position enables the bone 

 to act as a spring, modifying concussion and giving elasticity of step and 

 freedom from jar. The coronary bone (1>) rests entirely on the os pedis. 

 . The navicular bone (d), placed posteriorly, bears no weight, but gives 

 increased leverage power to the tendon (e). This bone, like the sesa- 

 moids, is a muscular appendage, and is not intended to support weight. 

 Compare with Fig. 92 on opposite page. 



tion of the cancellated structure of the navicular bone, 

 or of the cartilage on its inferior surface. It is caused 

 by the rheumatoid diathesis (taint), concussion, and change 



