FEATURES OF ANIMAL FOBM 



41 



chanically, by its presence, with the action of the part, 



all pain having subsided. In some instances, the process 



may automatically overcome the primary 



condition which caused it. If the ex- 

 ostosis constituting a spavin or a ringbone, 



for instance, becomes sufficiently extensive 



to obliterate the joint about which it has 



grown, thereby preventing all movement, 



the pain of motion in that part and the 



coincident lameness will be removed. This 



process is called anchylosis, and accounts 



for the fact that a great big so-called jack 



spavin may cause no lameness, while the 



most acute pain and lameness will attend 



an occult spavin when there is, as yet, 

 scarcely any enlarge- 

 ment. The joints in- 

 volved in both spavin 

 and ringbone are not 

 t' \ ^» ^^^ essential joints of those parts, and 

 they can, therefore, be dispensed with 

 and cause no serious interference with 

 function. Exostosis is usually a sequel 

 of or accompanies an inflammation of 

 the joint surface, called arthritis, as in 



£ 1-^^^^^^ spavin, although it may be independ- 

 ent of the joint, as in sidebone, and, 

 usually, in splint. The lameness due 

 at right normal leg to an arthritis is most marked when 



Fig. 13. — Leg 

 showing large 

 spavin. 



Fig. 14. — Leg show 

 ing ringbone at left 



in contrast. 



the horse is first taken out after a long 

 rest preceded by hard work, and gradually disappears 

 more or less as the horse " warms out of it." The pres- 

 ence of an exostosis is best made out by comparing the 



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