NAVICULAR DISEASE. 211 



6. Heredity, no doubt, has a strong predisposing influence; 

 but I have met with no proof that, of itself, it can produce the 

 disease. 



7. Direct injury may, in some rare instances, give rise to this 

 malady. Its influence must be extremely small, considering that 

 only two cases (see next paragraph) in the hind feet have been 

 reported. 



SPECIAL LIABILITY OF THE FORE FEET TO NAVICULAR 

 DISEASE. — The extraordinary difference in this respect between 

 the fore and hind feet (according to Moller, only two oases having 

 been recorded) cannot be accounted for by the fact which Col. F. 

 Smith puts forward, that horses, when standing, are accustomed io 

 rest their hind limbs, alternately, while remaining " level " in 

 front ; because, as I have already remarked, long-oontinued stand- 

 ing (of, for instance, from one to four months on board ship during 

 sea voyages) appears to have no influence in setting up navicular 

 disease ; although it is a very potent agent in bringing on laminitis. 

 Taking into consideration the large part played by concussion in 

 the production of navicular disease, I am convinced that the 

 difference in liability is chiefly, if not wholly, due to the fact that 

 far more concussion falls on the fore feet than on the hind feet. 



SYMPTOMS. — ^By actual examination of the foot, an observer 

 will discover little to indicate the nature of the ailment ; though 

 he may guess at its existence from the absence of signs of other 

 diseases. The peculiarity of the animal's gait, and the manner in 

 which the horse '' points," will tend to confirm his supposition. In 

 old cases, there is often contraction, at the heels, of the affected 

 foot or feet. Mr. Harold Leeney, M.R.C.V.S., regards a shrunken 

 condition of coronet as characteristic of navicular disease. In 

 laminitis, the opposite condition, namely, fulness, is generally to be 

 seen in the affected coronet. 



As a rule, the horse, in this disease, "points" by placing his 

 toe on the ground, raising his heel, and rounding his fetlock joint. 

 Sometimes, even in advanced cases, he does not point. 



The horse, generally, unless the case be bad, walks sound, 

 though when trotted he goes " short," " daisy cuts," and " digs 

 his toes into the ground; " the result of this last mentioned habit 

 being, especially if only one foot is affected, that the toe of the 

 shoe gets worn in a marked manner. Percivall observes that in 

 trying to save the heel, the animal turns the toe in. 



There are fewer cases of lameness from navicular disease now 

 than formerly, apparently from the following reasons: — (1) vete- 

 rinary surgeons perform neurotomy more frequently; (2) fewer 



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