POSTERIOR MEMBER. 



275 



FIG. 87. 



3d. Jarde. 1 Jarde (Fig. 87) is not, as every one wrongly believes, an osse- 

 ous tumor, reproducing identically, upon the external side of the hock, the 

 enlargement which a spavin forms on the internal side of the 

 same region. It is simply a more or less extensive periostitis 

 of the head of the external rudimentary metatarsal bone. This 

 lesion is very often complicated by a splint, as in the case 

 which we represent (Figs. 88 and 89) ; at other times, and this 

 is perhaps the most frequent circumstance, nothing is found 

 but a tumor developed at the superior and external side of the 

 canon, that is to say, a simple splint. This is at least the 

 opinion which we have acquired as the result of our re- 

 searches for a period of observation extending over more 

 than forty years, in conditions altogether exceptional in so far 

 as the abundance of the specimens studied was concerned. 



Jarde is never situated at the same height as spavin ; 

 it is always lower, which already implies that the external 

 tarsal bones are not the seat of it. Besides, it remains con- 

 fined outwardly or posteriorly, and does not extend forward 

 as spavin does ; finally, it is rather inclined to descend along 

 the rudimentary metatarsal than to ascend upon the cuboid 

 or the base of the calcaneus, additional reasons which mili- 

 tate in favor of its metatarsal origin. It should, therefore, neither in location, 

 lesions, nor gravity, be considered as the homologue of spavin. 



We also sometimes meet, on the outer side of the hock, a tumor localized 

 on the base of the calcaneus, the scaphoid, the cuboid, and the head of the 

 external metatarsal bone, a tumor sufficiently circumscribed to merit a special 

 name other than that of osteophyte, of which we shall speak farther on. (It 

 could be called external spavin.} 



In 1852, M. Gillet 2 represented the true jarcle with great exactness, although, 

 by a singular deference for the erroneous opinions of his predecessors and his 

 contemporaries, he would not abide by his own observations alone. His draw- 

 ing, altogether similar to our own (Figs. 88 and 89), differed, for good reasons, 

 from all the other more or less fantastic representations which have been made 

 of the blemish in question. We will add that it is very rare to meet lesions 

 of this nature, and we are certain not to be contradicted upon this point by those 

 who have taken the trouble to search for them. 



The anatomical facts explain why the periostitis of which we speak can 

 really only take its origin upon the head of the external splint bone and not 

 otherwise. It is necessary first to recall that exostoses resulting from usage 

 appear only at points of insertion of the large articular ligaments. It is at these 

 points that tractions and irritations are conveyed to the periosteum and inflame 

 it. The irritation, spreading little by little, invades ultimately all the bony sur- 

 faces covered by these ligaments. It is according to this process that curb, 

 spavin, and exostoses of the bodies of the vertebrae are produced ; this same pro- 

 cess we shall find again as the primary factor in the formation of splints or 



1 This is the "curb" of English authors. 



2 Gillet, Des Tares osseuses des membres du cheval, in Recueil de memoires et observations 

 sur Phygiene et la mgdecine v6terinaires militaires, t. iv. p. 317, chez Dumaine, Paris, 1852. 



