12 ON Till-: NAVICULAR DISKASE. 



ii.iinmginm- TIic occLilt 01' partial contraction abruptly op- 

 c.rt.'tulinrti'''' poses the navicular bone in its descent, and thereby 

 vicuia'dislase" crushes or bruises tlie delicate synovial membrane 

 lining the joint, which suffers a mechanical injury 

 from the very material which Nature bestowed as 

 a defence, and which has degenerated into a hard, 

 rigid, inelastic protuberance, no longer capable of 

 yielding and expanding under the superincumbent 

 weight. Nature has made ample provision to ward 

 off concussion from these parts in the colt or un- 

 shod foot ; for not only are the posterior parts much 

 more elastic, as compared with the toe and sides of 

 the foot, but she has also bolstered the navicular 

 joint with two elastic cushions placed one on the 

 other, and which, united, form such a hard and soft 

 medium, as no human ingenuity could imitate ; the 

 tough, though highly elastic, horny frog being op- 

 posed to the ground, and the fatty frog encompas- 

 sing the navicular bone and ilexor tendon, which 

 are further shielded by elastic cartilages. Now, as 

 all these parts, in a state of nature, preserve their 

 elastic properties, they yield and give room for the 

 navicular joint to play like a i)ullcy, without com- 

 pression or restraint, in the most violent exertions 

 of the animal. 



1 am thoroughly satisfied, that, n hen contraction 

 is accompanied widi chronic lameness, disease 

 exists in the navicular joint, either structural or 

 functional; and that this comi)lain(, at its com- 



