NAVICULAR DISEASE. 



207 



PREDISPOSING INFLUENCES.— 1. A naturally weak or de- 

 fective condition of hone, in the production of which the influence 

 of heredity is well marked. 



2. Altered nutrition of the hone due to chill from the practice of 

 standing on cold stones. This supposition seems, as pointed out 

 to me by Colonel C. Phillips, A.V.D., to be borne out by the fact 



Fig. 67. — Caries of the navicular bone 

 (navicular disease). 



Fig. 68. — Lower surface of pedal bone, Fig. 69. — Lower surface of pedal bone, with 

 showing attachment of perforans tendon, perforans tendon turned back, so as to 



which goes over the navicular bone. show caries of navicular bone. 



that a comparatively large number of troop horses in England are 

 annually " cast " for this complaint, which, in these instances, is 

 apparently brought on by the not uncommon practice, in cavalry 

 stables, of keeping the horses standing, the greater part of the day, 

 on bare stones, with not much more than an hour's exercise in the 

 twenty-four; while the ground upon which they parade and drill 



