DISEASES. 695 



The disease is principally seen in the fore feet, and more com- 

 monly in one foot alone; sometimes, however, both legs are 

 affected, one first, and the other following. Navicular disease of 

 the hind feet is seldom observed. 



It is accompanied with lameness and deformity of the foot, 

 and often proves rebeUious to treatment. It is followed by con- 

 traction of the heels {encastelure) which is itself often mistaken 

 for navicular disease. At any rate, the affections are nearly re- 

 lated, whether the disease of the sesamoid sheath, first occurring, 

 is followed by the contraction, or that the hoof, originally con- 

 tracted, gives rise to the subsequent alterations of structure 

 which constitute navicularthritis. At present we shall only con- 

 sider the deep inflammation of the podosesamoideal articulation, 

 occurring without primitive alteration in the form of the foot. 



I. Symptoms. — These are at first obscure. The lesion is 

 deeply situated, and is, so to speak, concealed in the hoof, which 

 itseK, is generally at first of very Hmited extent. The first symp- 

 tom which attracts attention is the lameness, which sometimes, 

 indeed, seems to be merely a certain weakness of the affected leg. 

 This lameness is at first intermittent and slight, but gradually in- 

 creases. When in the stable, the animal " points," that is, the dis- 

 eased foot is carried forward of a vertical Une, and assumes a 

 state of general relaxation of the muscles, with the coronet 

 straightened and the foot mostly resting on the toe. This in- 

 complete rest of the leg, which is sometimes kept in motion for- 

 ward and backward, becomes especially apparent if the animal is 

 moved backward in his stall. He then sets dovsTi his foot with 

 much hesitation, and for a short time ; the same thing also occurs 

 when, in order to relieve the opposite leg, the animal puts all his 

 weight on the diseased one. Still, a close examination of the foot 

 fails to reveal any marked lesion ; no change of form appearing, 

 no wain at the coronary band; merely a little heat toward the 

 heels, or on the frog, where there can also be found a certain 

 amount of low and deep sensibility, made apparent only by per- 

 cussion of the hammer upon the foot, or by the pressure with the 

 blacksmith's nippers, principally toward the heels and the frog. 

 According to Lafosse, the frog is often found indurated, atrophied 

 and thrushy. If exercised, the horse frequently stumbles, and 

 sometimes falls on his knees; he fears the pain of resting the 

 heels on the ground, and is limited in the movements of his knee 



