276 DISEASES OF BONE. 



Sidebones. 



NATURE. — Sidebones is the term used to express an ossified 

 condition of the lateral cartilages. The ossification may be partial 

 or complete, and may affect both cartilages, or only one. The 

 lateral cartilages are plates of cartilage mixed with fibrous tissue 

 which, on each side, are attached ito and placed above the wings 

 of the pedal bone. We may look upon them as cartilaginous and 

 fibrous prolongations, above and to the rear, of the wings of the 

 pedal bone. Fig. 105 gives us a representation of a pedal bone 

 from which the lateral cartilages have been removed; and Fig. 106, 

 that of the same pedal bone with these cartilages intact. In Fig. 

 107, which is a transverse and vertical section of a horse's foot, the 

 lateral cartilages can be seen as white curves. Each cartilage 

 in an ordinary saddle-horse is about 3 inches long, J inch in 

 thickness, and is about If inches high at the end of the wing of 

 the pedal bone, behind which it projects for about IJ inches. 

 These cartilages, which are peculiar to the horse family, are 

 attached to the plantar cushion (Figs. 61 and 70), which is a 

 fibrous and more or less elastic body that acts as a buffer between 

 the frog and the bones which are above it. The lower part of 

 the plantar cushion is covered by the sensitive frog, which is a 

 membrane that secretes the frog. The lateral cartilages are more 

 largely developed in the fore feet than in the hind feet. When 

 these cartilages are ossified, they usually present more or 

 less the appearance shown in Figs. 108 and 109. Sometimes only 

 the front part of the cartilage (at the quarters) becomes ossified, 

 as in Fig. 110, in which case the cartilages at the heels preserve 

 their elasticity. 



OCCURRENCE. — Sidebones are almost always confined to the 

 fore feet ; and in the majority of cases affect only cart-horses. I 

 think I may say that at least 50 per cent, of heavy draught 

 animals in large towns in England and Scotland suffer from them. 

 The outer cartilage is more frequently affected than the inner ; and, 

 according to Lungwitz, the near fore foot, than the off fore. Side- 

 bones are rarely seen in young horses which have not been put to 

 work. 



CAUSES. — The chief causes of sidebones appear to be : (1) de- 

 privation of frog pressure; and (2) injury. High calkins, the use 

 of which is almost entirely confined to cart-horses, deprives the 

 frog, to a great extent, of the natural support which it derives from 



