THE NAVICULAHrJOINT DISEASE. 389 



THE NAVTCULAR-JOINT DISEASE. 



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

 lame, and veterinary surgeons have been puzzled to discover the cause. The 

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

 practitioner may not have been able to discover an ostensible cause of lameness 

 in the whole limb. There is no one accustomed to horses who does not recollect 

 an instance of this. 



By reference to tho cut, e, page 345, 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 streng- 

 then 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. It is 

 very easy to conceive that, from sudden concussion, or from rapid and over- 

 strained motion, and that, perhaps, after the animal has been sometime at 

 rest, and the parts have not adapted themselves for motion, there may be 

 too much play between the bone and the tendon the delicate membrane 

 which covers the bone, or the cartilage of the bone, may be bruised, and in- 

 flamed, and destroyed ; that all the painful effects of an inflamed and opened 

 joint may ensue, and the horse be irrecoverably lame. Numerous dissec- 

 tions have shown that this joint, formed by the tendon and the bone, has been 

 the frequent, and the almost invariable, seat of these obscure lamenesses. The 

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

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

 become carious or decayed, and bony adhesions have taken place between 

 the navicular and the pastern and the coffin-bones, and this part of the foot has 

 often become completely disorganised and useless. This joint is probably the 

 seat of lameness, not only in well-formed 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 is absorbed by that pressure, and the sole is 

 become concave, and the horny frog, and the coffin-bone too, thereby elevated, 

 there will 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 

 farther 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 indisposed for it, and he is then suddenly and violently exercised, 

 this membrane is very liable to be bruised and injured. This, amongst other 

 evils, will be lessened by a loose box, in which a horse will always take some 

 exercise *. 



* To Mr. James Turner the veterinary pro- unfrequently before they are five years old. 

 fession is indebted for a knowledge of the seat This contraction is not, ho\yever, necessarily 

 and cause of this lameness. In the year 1816 connected with lameness a large proportion 

 he first alluded to it, and the truth and 5m- of horses in the very midst of labour are pcr- 

 portanco of his discovery is now universally fectly free from lameness, 

 allowed. The next deviation from nature is the pas- 

 According to Mr. Turner, contraction of the sive state to which the foot is submitted at 

 hoof is more or less apparent in the majority least twenty-two or twenty-three hours out of 

 of horses that have been accustomed to be the twenty-four, and sometimes for several 

 shod. This is often long before they have consecutive days. Let this be compared with 

 attained the highest value for work, and not the few hours during which the feet of a hcrse 



