298 THE HORSE. 



THE NAVICULAR-JOINT DISEASE. 



Many horses with well-formed and open feet become sadly and permanently 

 lame; and veterinary surgeons have been much puzzled to find out why. 

 The farrier has had his convenient explanation " the shoulder ;" but the 

 scientific practitioner has not been able to discover an ostensible cause of 

 lameness in the whole limb. There is no one accustomed to horses who 

 does not recollect many an instance of this. Mr. James Turner has, of 

 late years, thrown very considerable lijrht on the seat and cause of this 

 disease, although, as in contracted feet, the most skilful surg-eon will rarely 

 effect a cure. 



By reference to our cut, e, page 249, it will be seen that, behind and 

 beneath the lower pastern-bone, and behind and above the heel of the coffin- 

 bone, is a small bone called the navicular or shuttle bone. It is so placed 

 as to strengthen the union between the lower pastern and the coffin-bone, 

 and to enable the flexor tendon, which passes over it, in order to be inserted 

 into the bottom of the coffin-bone, to act with more advantage; it forms a 

 kind of joint with that tendon. There is a great deal of weight thrown on 

 the navicular-bone, and from the navicular-bone on the tendon ; and there is 

 a great deal of motion or play between them in the bending and extension 

 of the pasterns. Now it is very easy to conceive that from sudden con- 

 cussion, or from rapid and overstrained motion, and that perhaps after the 

 animal has been some time at rest, and the parts have not adapted them- 

 selves for motion, that there may be too much play between the bone and 

 the tendon ; that the delicate membrane which covers the bone, or the 

 cartilage of the bone, may be bruised, and inflamed, and destroyed ; and 

 that all the painful effects of an inflamed and opened joint may ensue, and 

 the horse may be dreadfully lame. Numerous dissections have shewn that 

 this joint, formed by the tendon and the bone, has been the frequent, and, 

 we believe it to be, the almost invariable seat of these obscure lamenesses. 

 Tlie membrane covering the cartilage of the bone has been found in an 

 ulcerated state ; the cartilage itself has been ulcerated and eaten away ; and 

 the bone has become carious or decayed, and bony adhesions have often 

 taken place between the navicular and the pastern and the coffin-bones, and 

 this part of the foot has become completely disorganised and useless. This 

 johit is probably the seat of lameness, not only in flat and perfect feet, but 

 in those which become lame after contraction ; for in proportion as the inner 

 frog is compressed by the contraction of the heels, and the frog is absorbed 

 by that pressure, and the sole is become concave, and the horny frog, and 

 the coffin-bone too, thereby elevated (see cut, page 269), will there be less 

 room for the action of this joint, and more danger of the tendon and the 

 delicate membrane of the navicular-bone being crushed between that bone 

 and the horny frog. 



Stable management has little to do with the production of this disease, 

 any further than if a horse stands idle in the stable several days, and the 

 structure of the foot, and all the apparatus connected with motion, become 

 unused to exertion, and indiaposed for it, and he be then suddenly and vio- 

 lently exercised, this membrane is very liable to be bruised and injiued. 

 Irregular and undue exercise are the causes in all feet ; but the contracted 

 foot, from its alteration of form, is most in danger. 



The cure is extremely uncertain. The first object is to abate the intlam- 

 mation in this very susceptible membrane. LocaJ bleeding, poulticing, 

 and physic will be our principal resources. If there be contraction, this 

 must, if possible, be removed by the means already pointed out. If there 

 be not contraction, it will be prudent to remove all surrounding pressure 



