DISEASES OF THE HOCK. 305 



The hereditary predisposition to hone-spavin is heyond douh(^ 

 all writers of authority being agreed upon the point, -which is 

 also well known to breeders of horses. This hereditary pra- 

 disposition is not always due to peculiarity of conformation, 

 as many breeds or families of horses with well-formed hocks 

 often become unsound from this cause. Peculiarity of confc- 

 mation is nevertheless not only hereditary, but is of itself a pre- 

 disposing cause of spavin. 



Percivall says — " I am very much disposed to believe in the 

 existence in the system of what I would call an ossific diathesis. 

 I have most assuredly seen unbroke colts so prone in their 

 economy to the production of bone, that, without any assignable 

 outward cause — without recognisable injury of any kind — they 

 have at a very early age exhibited ring-bones, and splints, and 

 spavins. There might have been something peculiar in the 

 construction of their limbs to account for this ; at the same 

 time there appeared a more than ordinary propensity in their 

 vascular system to osseous effusion. Growing young horses — 

 and particularly such as are what is called " overgrown " 

 — may be said to be predisposed to spavin, simply from the 

 circumstance of the weakness manifest in their hocks, as well as 

 other joints. When horses whose frames have otitgrown their 

 "strength, with their long and tender limbs, come to be broke — 

 to have weight placed upon their backs at a time when the 

 weight of their own bodies is as much as they are able to bear 

 — then it is that the joints in an especial degree are likely to 

 suffer, and wind-gall and spavin to be the result. Indeed, under 

 such circumstances, spavin, like splint and other transformations. 

 of soft and elastic tissue into bone, may be regarded as nature's 

 means of fortification against more serious failures." 



These remarks of Percivall are based upon correct observa- 

 tions, and one cannot help admiring the way in which they 

 are put before the reader. There is not one point that I c&.\ 

 difiptcte, tmless, indeed, the term osseous effusion, which may 

 not now be looked upon as being consistent with correct patho- 

 logical knowledge. 



The local or exciting causes of spavin are sprains of the liga- 

 ments, more particularly the inter-osseous, and concussion of the 

 bones. The old writers ascribed spavins to -blows ; so unlikely, 

 however, is the seat of them to receive a blow, that there need 



