DI3SA5S5 07 TSE HOCK. oil 



DISEASES OF THE IJGAMENTOUS AND TENDINOUS STRUCTURES OP 



THE HOCK." 



Tlwrcni/jh-pin is a bursal enlargement situated on the inferior 

 lateral aspect of the thigh and upper and posterior part of the 

 hock, arising from disease of the tendon of the flexor pedis pov- 

 forans muscle, which is enclosed in a synovial sheath, on the 

 inner side of the os calcis, or from dropsy of the sheath, without 

 disease of the tendon. The fluid which fills it may, by pressure, 

 be forced from one side to the other ; hence the terra thorough- 

 pin, or running through from side to side. This may bo 

 described as true thorough-pin, in contradistinction to that 

 as?ociated with very large bog-spavins. 



A thorough-pin, however large, does not cause bog-spavin, as 

 there is no real channel of communication between the true hock- 

 joint and the bursa of the perforans tendon ; but the capsule of 

 the joint swells upwards and backwards, bulges into the bursa 

 of the tendon, and a large bog-spavin may thus cause the dis- 

 tension of the bursa, and the appearance of thorough-pin. 



Thorough-pins are generally found in short, flesliy, upri<^ht 

 hocks, where the os calcis is short and ill developed. We can 

 account for such hocks being subject to them by the knowledge 

 that the lever of the limb being a short one, more strain is 

 thrown upon the flexor ^tendons, the flexors of the foot beinf» 

 icxtensors of the hock. 



Tig. 54.— Spring truss Tor thorongh-pi'ii and bog-spavin, designed 

 by Mr. Broad, Bath. 



Eailway shunt liorses are very liable to fall unsound from 

 thorough-pin, in consequence of the very heavy truck loads they 

 Jiave to start. 



Ju the treatment of thorough-pins and bog-spavins, rest, Iha 



