210 DISEASES OF THE FEET. 



rarity, behind, in comparison to its frequency in front, proves 

 almost conclusively that the production of this malady by sprain 

 of this tendon is an accident which very seldom takes place. I 

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

 tion which showed the existence of sprain or laceration of the 

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

 and which also showed that the navicular bone was in a healthy 

 state ; but 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 any way. I therefore submit that 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 high-heeled shoes or calkins. This alleged 

 cause may be dismissed; for were it valid, we should find that 

 the animals which are most commonly shod with calkins — namely, 

 heavy cart-horses — are those which are 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, 

 we should certainly have many more cases of this malady in 

 the hind feet, than the two isolated instances (p. 211) met mth in 

 many thousands, especially as horses are almost always shod 

 higher behind than in front. Besides, a horse suffering from 

 navicular disease " goes on the toe " as a rule, which is a style 

 of progression he would hardly adopt, if the disease had been 

 brought on by identically the same course of action (raising the 

 heel from the ground) by which he now strives to relieve the 

 inflamed parts from pain. Also, a horse thus affected, almost 

 always goes better in a high-heeled shoe, than in a low-heeled 

 one; because, raising the heel tends to flex the pedal joint, and, 

 consequently, to relieve, to some extent, the inflamed structures 

 from the painful pressure of the perforans tendon. 



4. Compression. The degree of compression on the navicular 

 bone is affected by the rate of speed, and by the weight of the 

 rider or of the conveyance ; but not by the nature of the ground. 

 Consequently, if compression was the chief cause of this disease, 

 racehorses, chasers, hunters, and heavy cart-horses (especially 

 those which wear " toe pieces" to their shoes) would be the chief 

 sufferers. On the contrary, they are all but exempt ! 



5. Rheumatism. Beyond the supposition that chill, as we have 

 seen (p. 207), has a predisposing influence, I know no argument 

 which would support the theory that rheumatism can originate this 

 disease. 



