900 OSSIFICATION OF THE LATERAL CARTILAGE. SIDE-BONE. 



end of the cartilage, where disease usually commences. Mechanical 

 injury is another undoubted cause. This, and the fact that the 

 outer half of the foot suffers the greater shock during movement, 

 explains why the outer cartilage more frequently becomes ossified 

 than the inner. 



The prognosis depends on the horse's work, weight, and breed, 

 on the form of the hoof, and on the extent of ossification. Heavy 

 horses with completely ossified lateral cartilages and contracted 

 hoofs are of little use for rapid work on paved streets ; though horses 

 with large side-bones and feet of good shape may work satisfactorily 

 for many years. When only one cartilage is affected, or when the 

 animal is worked on soft ground, side-bones are comparatively 



Fig. 515. — Pedal bone, with almost complete ossification of the lateral cartilages. 

 a, Pedal bone ; b, wing of pedal bone, from which point, as a rule, ossification 

 commences ; c, articular surface ; d, rough, uneven surfaces of the ossified 

 cartilages. 



unimportant. While ossification is in active progress the animal 

 goes tender, if not actually lame, but as soon as it becomes complete 

 the lameness tends to disappear, though it readily returns in conse- 

 quence of bruising or strain if the tread is not level. Lameness is 

 usually temporary, but the diseased cartilage can never be restored 

 to its primitive condition. 



After ossification is complete, lameness may be produced by 

 bruising of the sensitive laminae, which are then enclosed between 

 two hard, unyielding structures — the horny wall and ossified 

 cartilage. The plantar cushion may also suffer from being more or 

 less confined between the ossified cartilages. If, in addition, the 

 wall of the hoof is contracted at the heels, the condition is even more 

 serious. In estimating the effect of the pressure on the sensitive 

 laminae, the fact that only the inferior half of each cartilage is covered 

 by keratogenous membrane should not be overlooked. 



