1000 DISEASES OF THE HOCK. 



the observer takes up a position either some stops in front of or 

 behind the horse, and compares the inner surfaces of the hocks. In 

 this way experts can detect the slightest differences, though it is 

 by no means possible to determine by this examination alone 

 whether or not spavin exists, especially in well-bred horses, whose 

 hocks are seldom absolutely symmetrical. But even in other 

 animals a want of symmetry in the hocks cannot of itself be regarded 

 as a certain sign of spavin. The terms " coarse," &c, used in speaking 

 of formation, are tacit acknowledgments of this fact, and are often 

 only circumlocutions for spavin. 



(3) The above signs of spavin are often accompanied by atrophy 

 of the muscles of the quarter, as usually happens in chronic painful 

 lamenesses. Eberlein also states having been able to demonstrate 

 atrophy of the diseased hock by actual measurements. The upper 

 part of the affected joint was sometimes 2 inches less in diameter 

 than that of the sound one. Even at the level of the exostosis (spavin) 

 the measurement was lessened. Eberlein regards this as due to 

 atrophy of inaction. 



The visible superficial changes usually show whether the joint is 

 or has been diseased, but alone are not proof that the existent 

 lameness is due to spavin, for very frequently the lameness disappears 

 after anchylosis of the joint, though other conditions may interfere 

 with the movement of the limb. To refer such lameness to the changes 

 in the hock-joint would be a serious error. 



The diagnosis " spavin lameness " is justified when : — 



(1) The local changes are accompanied by lameness, the course 

 and other peculiarities of which agree with the description above 

 given. 



(2) Muscular atrophy or other condition points to old-standing 

 lameness, probably connected with the anatomical changes. As 

 already stated, exostoses are more likely to cause lameness the nearer 

 they lie to the front of the joint. Sometimes traces of past treat- 

 ment are visible, pointing to a chronic condition, and supporting the 

 diagnosis " spavin. 1 ' 



Acute inflammatory symptoms, increased warmth, pain on 

 pressure, &c, are seldom met with unless the condition has resulted 

 from violence, but their presence is not incompatible with spavin 

 lameness. 



Differential diagnosis. By bearing in mind the above-mentioned 

 principles, mistakes will usually be avoided, though the following 

 conditions should be considered : — 



(1) Stringhalt. a disease which will be described in another place, 



