236 LAMENESS OF THE HORSE 



and inferior portion of the liock. There is also included under 

 this name, articular inflammation wherein no external evidence 

 is shown. Spavin lameness has long been recognized and much 

 has been written upon this subject. Since authorities are agreed 

 that most cases of lameness in the hind leg are due to hock 

 affection, and because the majority of cases of lameness which 

 have the tarsal region as the seat of trouble are instances of spa- 

 vin lameness, this disease merits all the attention it has received. 



Etiology and Occurrence. — Causes may well be classified as 

 predisposing and exciting, for there are many etiologic factors 

 to be reckoned with in spavin, some of which are widely different 

 in nature. 



Considered as predisposing causes, hereditary influences play 

 an important role and may, owing to faulty conformation, sub- 

 ject an animal to affections of this kind because of dispropor- 

 tionate development of parts (weak and small joints and heavy 

 muscular hips) ; or as a consequence of inherited traits, a sub- 

 ject may manifest susceptibility to degenerative bone changes 

 which are signalized by the formation of exostoses of different 

 parts on one or more of the legs. Hereditary predispositions 

 make for the presence of spavin in a large percentage of the 

 progeny of sires so aft'ected. This fact has been repeatedly 

 demonstrated in this country as well as elsewhere according to 

 Quitman, Dalrymple and Merillat.^ A number of states have 

 passed stallion inspection laws stipulating that animals having 

 such exostoses as spavin and ringbone cannot be registered ex- 

 cept as ''unsound." 



Asymmetrical conformation, particularly where the hock is 

 obviously small and weak as compared with other parts of the 

 leg, constitutes a noteworthy predisposing cause. 



Peters' theory is plausible that the screw-like joint between 

 the tibia and the tibial tarsal (astragulus) bones causes these 

 structures to functionate in a manner not in harmony with the 

 provisions allowed by the collateral ligaments of the tarsus, per- 



iDiscussions on paper entitled "The Spavin Group of Lamenesses," hy W. L. 

 Williams, Carl W. Fisher and D. H. Udall, Proceedings of American Veteri- 

 nary Medical Association, 1905. 



