NAVICULAK DISEASE. 



209 



"going" is siiKiother, softer, imd, cousequently, less prodvictive of 

 concussion. 



2. Sprain of the perfitidiis tenduii at the point at wiiicli it 

 passes over the navicular bone. The fact that the perforaiis tendon 

 of the hind limb enjoys no special immunity from sprain, taken 

 conjointly with the fact that navicular disease is of extreme 

 rarity behind, in comjiarison to its frequency in front, jjroves 

 almost conclusively that the production of this malady by sprain 

 of this tendon is an accident which very seldom takes plac-tj. I 

 have never seen or heard of a single case of post-mortem examina- 

 tion which showed the existenc-e of sprain or laceration of the 

 portion of the perforans tendon that works over the navicular bone, 

 and also showed that the navicidar bone was in a healthy state; 



Long f\asUm bent 

 PasUm jouiV 

 Extensor Icndtm offool 

 Short pastern bane . 

 Pyramtdal process.. 



Peaal joint 



Sm-fitu'i lamina 

 Peual ham .. 

 ftuiX of 



PaUalhOTU 



Perforans 



' tendon 



J'trTaratu.'^ tendmv 



Iniertion cfiitrfaratus 



\aA/icnIar bon£. 



Plantar cushi n 



Fig. 70. — Vertical and longitudinal section of horse's fool. 



Imt I have met with several cases of recent navicular disease which, 

 by examination after death, disclosed a diseased condition of the 

 navicular bone without the tendon or synovial bursa being 

 affected in a.nj way. The foregoing considerations demonstrate 

 the fact that, in the vast majority of instances, the starting point 

 of navicular disease is in the bone or in the articular cartilage 

 which covers its lower surface, and not in the tendon or bursa. 



3. Employment of higlt-lieeled shoes or calkins. This alleged 

 "cause may be dismissed , for were it valid, the animals which are 

 most commonly shod with calkins — namely, heavy cart-horses — 

 would be those peculiarly liable to the disease in question ; a 

 supposition that is absolutely incorrect. Again, were the practice 

 of using high heels or calkins to blame, there would certainly be 

 many more cases of this malady in the hind feet, than the two 

 i.solated instances (p. 210) met with in many thousands, especially 

 a.s horses are almost always shod higher behind than in front. 

 Besides, a horse suffering from navicular disease " goes on the 



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