DISEASES OF BONES 



217 



BONE-SPAVIN 



A bony outgrowth on the inner and lower part of the hock is termed 

 a bone-spavin (fig. 324). 



The enlargement usually appears towards the front, but it may occupy 

 a backward position, or extend from front to back. Spavins vary in size 

 as well as in position. Sometimes they are small and with difficulty 

 identified, at others they 

 reach a considerable size. 

 The same variation ap- 

 pears in respect to form. , 

 They may present them- 

 selves as rounded, or more 

 or less pointed and ir- 

 regular swellings, or as a 

 projecting ridge, extend- 

 ing across the hock from 

 back to front. Usually 

 they appear on one hock 

 only, but frequently both 

 are affected either simul- 

 taneously or consecu- 

 tively. Hocks of every 

 variety of size and confor- 

 mation, from the biggest 

 and best to the smallest 

 and weakest, are liable 

 to become affected, but it goes without saying that the disease is most 

 frequently found in the latter. 



Causes. — The predisposition to spavin is unquestionably hereditary. 

 Horses with straight quarters and upright pasterns seem especially liable 

 to it. Sjirain and concussion to the joint, acting separately or together, 

 are the exciting causes, and there is reason to think that these accidents 

 are more especially likely to occur when animals are forced in their work 

 under circumstances of fatigue and want of condition and development. 

 The outward enlargement is an evidence of the inflammation going on in 

 the articular surfaces of the bones. 



The great variation found to exist in the conformation of the hocks 

 of different horses, and indeed sometimes in the two hocks of the same 

 horse, has ever been a stumbling-block to the veterinarian in the diagnosis 



Fig. 324. — Bone-Spavin. A, Spavin. 



