NAVICULAR-JOINT DISEASE. 291 



joint oil. This fluid is of all importance ; for, if it 

 be deficient, the sides of the sac, not being- properly 

 distended, rub against and chafe one another. In- 

 flammation follows ; with it comes lameness. Pain is 

 then great, and the horse rests his foot; thereby 

 aggravating the disorder by not stimulating the syno- 

 vial sac to secrete the joint oil; and by degrees ulcera- 

 tion of the lower side of the navicular bone is in- 

 duced. This may go on for a long time; the horse 

 being sometimes so lame that in mercy he is ultimately 

 destroyed. In other instances, however, the animal 

 lives; adhesion takes place between the tendon and 

 the bone: the horse is no longer lame; but he steps 

 short and is incurably groggy. 



The cause of navicular disease is any thing which 

 may lessen the secretion of the joint oil between the 

 bone and the tendon. Too much rest; too much 

 work; too violent exertion; or concussion to the foot; 

 each and all may be the means of setting up this fear- 

 ful disorder. 



The horse with navicular disease is lame, and the 

 lame foot is hot. The animal, to take the weight from 

 it, stands pointing it in the stable; he holds the lame 

 leg more forward than the sound one ; for navicular 

 disease is not known to exist in the hind feet. These 

 symptoms are not, however, constant; but in the early 

 stage of the disease they vary. The heat is some- 

 times lost ; sometimes the foot is of its natural warmth; 

 and sometimes it is deadly cold. Sometimes the horse 

 is very lame ; goes out lame ; after a little work travels 

 sound ; and sometimes his pace is as firm as though he 

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