274 



THE EXTERIOR OF THE HORSE. 



Fig. 86. 



most usually certain bones of the tarsus and of the metatarsus covered by the 

 expansion of the inferior extremity of the internal lateral ligament of the ar- 

 ticulation, — that is to say, the head of the rudimentary metatarsal bone, a small 

 portion of the principal metatarsal, the cuneiforms, the 

 scaphoid, and even the base of the astragalus. Frequently, 

 however, it is much more circumscribed, which has led H. 

 Bouley to specify as metatarsal, or low, the spavin which is 

 situated at the upper extismity of the canon, and as tarso- 

 metatarsal, or high, that v'hich affects the bones of the tarsus 

 as well as those of the metatarsus. 



The first is manifested externally as an exaggeration of 

 the eminence formed by the head of the internal splint 

 bone, or, again, when it is more anterior, by the greater vol- 

 ume of the tuberosity of insertion of the flexor muscle of the 

 metatarsus. Sometimes it is complicated by a splint on the 

 canon, in consequence of the abnormal ossification of the in- 

 terosseous ligament which unites the rudimentary to the 

 principal metatarsal bone. Whatever may be its exact seat 

 and its volume, which are susceptible to variation, metatarsal 

 spavin ordinarily occasions only a temporary lameness, which 

 ceases, in most instances, after a certain lapse of time, when 

 the work of ossification is completed. 

 As to tarso-metatarsal spavin, its gravity is very different and its frequency 

 much greater. It constitutes, in fact, a kind of exostosis which solders the inferior 

 bones of the tarsus to one another and to the metatarsus. It is at first limited to 

 the periphery of the articular margins, but progressively invades the articular 

 surfaces themselves. The latter complication, whose evil effects are easily under- 

 stood, — in one word, true anchylosis, — does not always exist, even in the case 

 of very voluminous exostoses. We have examined the articular surfaces in a 

 number of instances in old horses, and found them still intact. Such a lesion 

 does not, as can be perceived, completely annihilate the movements of the tarsal 

 articulations, and, consequently, lessens the gravity of the prognosis which may 

 have been deduced from it. 



Bone spavin, at the beginning of its formation, and before the appearance 

 of the external tumor, determines a lameness, generally very intense, upon the 

 nature of which it is almost impossible to decide with certainty. The lame- 

 ness which follows has no pathognomonic character, even when it is accompa- 

 nied by the jerk of string-halt. It is only at the end of a certain time that the 

 exostosis is manifested in profile upon the internal side of the hock. Its volume 

 and its seat are, in such cases, very variable. Sometimes scarcely distinct, some- 

 times very well defined, it projects inward, forwa/d, or backward from the ar- 

 ticulation. In rather frequent cases the lameness at this period diminishes in 

 intensity or disappears entirely ; but in most instances it persists and remains 

 in relation with the extent of the tumor. Its characteristics are no longer the 

 same ; the animal suffers less pain and the limp seems to be due more to the 

 mechanical difficulties which the tarsal bones experience in their displacements. 

 However it may be, it is apparent that the gravity of the prognosis varies with 

 the nature of the articular lesions, the obstacles offered to locomotion, and the 

 persistence and tenacity of the rational symptoms to which the blemish is heir. 



