NAVICULAK DISEASE. 339 



this dryness of the bursse be present or not, it is very true that 

 want of exercise is a powerful predisposing cause of the disease, 

 and, doubtless, its effects are due to the localisation of a consti- 

 tutional tendency to rheumatoid bursitis — (See Eheumatoid 

 Arthritis.) Tlie other accidental causes are pressure of a stone 

 in the foot, impacted immediately below the bursa, and exciting 

 inflammation; punctures, and allowing the toe of the foot to 

 attain an inordinate length. The most frequent predisposing 

 cause being the abnormally relative position of the phalangeal 

 bones, either arising from congenital formation of limb, or 

 induced by shoeing with thick-heeled shoes ; the exciting cause 

 must be looked for in the pace. Eace-horses, so long as they 

 are shod with racing shoes, rarely suffer from navicular disease. 

 The pace with them teUs upon the column of weight-bearing 

 bones and upon the ligaments and tendons, but when put to 

 Jiarness-work, in carts, omnibuses, &c., and shod with thick shoes, 

 they soon become unsound. 



Hunters, again, are not nearly so prone to become lame from 

 navicular disease as harness-horses ; but if strain were the cause, 

 they would be continually falling lame. They are, however, 

 shod with a level shoe, which allows the frog to touch the 

 ground, and the great concussive shocks, which would be other- 

 wise inflicted at every jump the animal is called upon to take, 

 are thus modified or destroyed. 



At one time I was of opinion that compression was the cause ; 

 that the tendon caused so much pressure upon the bone as to 

 produce irritation, and gave the animal a feehng of uneasiness 

 in the first instance, as evidenced by "pointing of the foot" 

 before lameness was apparent. I am, however, forced to abandon 

 this supposition, and to come to the conclusion that " pointing " 

 indicates a condition of ostitis sufficient to excite a feeling in 

 the horse that something is wrong, which is insufficient to cause 

 actual lameness. 



Symptoms. — The lameness is manifested in two ways : — Is^ 

 Suddenly, and perhaps without apparent cause, very often im- 

 mediately after the horse is newly shod. It is then attributed 

 to some fault in the nailing ; but on examination, nothing wrong 

 is found in the nailing, or that the shoe has bruised the foot in 

 any part by undue pressure. After a time this lameness may 

 disappear, or it may disappear from one foot, and after an iu- 



