SYMPTOMS OF NAVICULARTHRITIS. 161 



are also now, generally speaking, strikingly conspicuous. There 

 will likewise be felt some callous or osseous enlargement of the 

 coronet and pastern, and perhaps of the cartilages at the heels 

 as well ; it being about this period that ossific changes are com- 

 mencing. 



At the time that the examiner, standing directly in front of the 

 lame horse, is noticing these differences in the two fore hoofs, 

 most likely his eye will be attracted upwards by the manifest 

 flatness of surface, and apparent deficiency in substance, in the 

 shoulder of the same limb, as compared with that of the sound 

 one. So remarkable is this defalcation in cases in which pain 

 and lameness have long been present, that, considering the ob- 

 scurity in which the disease of the foot was years ago veiled, we 

 cannot feel surprised that the shoulder should have been regarded 

 as the actual seat of the lameness. We now, however, know 

 better. We know that the shrinking or wasting away of the 

 shoulder is but the natural consequence of lengthened repose 

 of the part, or comparatively inadequate action of its muscles ; 

 it being an established law in the animal economy that muscles be- 

 come large and bulky in proportion as they are exerted, and vice 

 versa. So that while the muscles of the lame limb are shrinking 

 for want of action, those of the sound limb are actually swelling 

 into larger size from having extra duty to perform : the circum- 

 stance of the shoulder evincing this change more than any other 

 part, and of one muscle in particular — the triceps extensor hrachii — 

 striking our attention from its diminished bulk, arising simply from 

 the shoulder being the most muscular part of the fore limb, and 

 from that muscle being used in action, as well as standing, more 

 than any other. Hence it happens that the fleshy prominence so 

 conspicuous over the joint of the elbow in the sound limb is fre- 

 quently hardly observable after long-continued lameness. 



Generally speaking, relapses of lameness, as I have had occasion 

 before to remark, take place in the foot first attacked by navicul ar- 

 thritis. Now and then, however, the opposite fore foot will become 

 attacked, and the disease, returning first in one foot and then in the 

 other, will exhibit a sort of gouty or metastatic character ; though 

 this, be it noted, is comparatively rare. When lameness attacks 



VOL. IV. Y 



