BONE SPAVIN 



513 



adjacent external sui-faces of the tarsal bones, always sliowing itself at the 

 inner side of the hock joint, on the scaphoid and cuneiform bones, and ex- 

 tending to the head of the internal small metatarsal bone. As in the case 

 of splint, the occurrence of exostosis on the internal rather than on the 

 external side of the hock has been accounted for by the supposition that 

 increased Aveight is thrown upon the internal small metatarsal bone, from 

 the turning up of the outer heel of the shoe, which is the common practice 

 of smiths. It appears to me, however, that the contrary is the case, and 

 that tliough more stress is laid upon 

 the foot on that side, there is less 

 weight on the inner side of the hock, 

 which has a tendency to spring open 

 in that direction. This will cause a 

 strain upon the ligaments connecting 

 the tarsal bones, and nature coming 

 to their aid throws out bone, which 

 ultimately substitutes anchylosis for 

 ligamentous union between these bones. 

 In all the actions of the hind-leg, from 

 the natural shaj)e of the hock, and 

 more especially in those horses which 

 are naturally " cow-hocked," there is 

 a tendency to yield inwai'ds rather than 

 in the opposite direction. The con- 

 sequence is that there is more strain 

 upon the ligamentous fibres which con- 

 nect the scaphoid with the two cunei- 

 form and the internal metatarsal, than 

 upon those uniting the cuboid with 

 the OS calcis and external metatarsal 

 bone. Hence, although exostosis does 

 sometimes show itself in other parts of 

 the tarsal bones, it here, as in the fore- 

 leg, is almost always confined to what 

 is called the "spavin place," namel}^, the 

 contiguous surfaces of scaphoid, cunei- 

 form, and internal metatarsal bones. In 

 very bad cases the articular cartilage 



becomes involved, and there is not only an external casing of new bone, but 

 the internal surfaces absolutely coalesce or anchylose. 



Symjdoms. — Lameness is an almost invariable symptom at the commence- 

 ment, and may continue throughout the life of the animal. As a rule, the 

 pain and consequent lameness is most manifest wlien first coming out of the 

 stable or after a rest. Many horses continue to do useful work though 

 spavined, as they " warm up " as it is called, and throw off all symptoms of 

 pain when they have gone a little way, as many an inexperienced purchaser 

 has learned to his cost ; though he may not have " swopped horses in crossing 

 a stream," he may have purchased a horse with spavin that comes out dead 

 lame after the day of the fair at which he was sold. 



In the early stages of this afiection it is often difficult to detect, and 



Fia. ?5. — Antero-internal View of Exosiosij 



CONSTITL'TINU SPAVIN. 



1. Os scaplioides. 



2. Os cuneifoniieparvum. 



3. Morbiil growth of bone, constituting 



disease known as bone spavin. 



4. Large metatarsal or cannon bone. 



the 



