NAVICULARTHRITIS— NAVICULAR DISEASE 391 



especially is this the case with regard to horses which are confined to the 

 stable in a standing position for long periods, while receiving large quantities 

 of highly stimulating food. 



The exciting cause is almost invariably due to concussion acting upon 

 feet deprived of their elasticity by long-continued abuse. Animals with 

 high hammerino; action suffer most, but long-continued wear on hard roads 

 affects all alike. The most sudden and acute cases are found among hunters 

 as the result of encountering deep drops in jumping into hard roads under 

 heavy weights. 



Symptoms. — As we have seen, under ordinary circumstances navicular 

 disease is slowly progressive, while in others it is sudden in attack, and 

 runs from the first a more or less acute course. In the former case the 

 onset of the disease is hardly perceptible. If in a riding horse, the first 

 indication of the oncoming aftection is mostly experienced by the rider, who 

 recognizes a sense of discomfort in the animal's movements arising out of 

 a loss of his ordinary elasticity and firmness of tread; but even this for a 

 time is subject to variation, so much so, that the owner may be led to 

 doubt the truth of his own impressions. As time goes on, however, 

 evidence of another kind soon presents itself The animal is noticed to 

 move feelingly, at first on one limb only, then after a while on the other, and 

 then on both; but it is rarely that the defect of action is uniform on the 

 two sides. To-day it is worst on the near one, when the animal is induced 

 to relieve it by throwing the weight of the body mainly on the off. This, 

 however, soon results in aggravation of mischief in the latter, when the 

 lameness becomes worse than in the former one, and so the relative severity 

 of the disease alternates from time to time between one limb and the 

 other. 



As to the character of the lameness, it is peculiar in the increasing 

 shortening of the stride, the gradual loss of knee action, and tendency to 

 move the entire limb in a stiff and stilty fashion. The action altogether 

 becomes short and wanting in liberty, and especially so on hard ground. 

 On a soft surface when relieved of concussion it is less marked, but in 

 advanced cases still evident even to the inexperienced eye. 



The lameness in navicular disease is seriously aggravated by work, and 

 is very pronounced on the morning following an active day. Moreover, as 

 the disease becomes established, there is a disposition in the animal to 

 relieve the heel of the foot from pressure and to throw it towards the toe. 

 This has the effect of occasioning tripping and stumbling, and rendering the 

 horse disagreeable if not actually unsafe both to ride and to drive. 



Still further evidence of the existence of navicularthritis may be found 

 in changes taking place in the form and character of the feet. Here it is 



