168 NAVICULARTHRITIS. 



negative as well as positive, that the navicular bursa or joint, 

 and that alone, was the seat of the obscure disease, and the sole 

 and exclusive source of the lameness. " The coffin joint is nevei^ 

 affected," says Mr. Turner : adding, *' I have dissected all the 

 groggy feet I have been able to procure, and have found the 

 navicular joint diseased in every instanced 



It is not difficult to find reasons why this discovery was not 

 made prior to the institution of a veterinary college, though it is 

 any thing but creditable to such an institution that it remained 

 unmade after the anatomy and pathology of the horse were pub- 

 licly professed to be taught. Deeply and cunningly buried as the 

 navicular joint is within the hoof, surrounded on every side by 

 bulwarks of the strongest description, we have no right to marvel 

 that the farriers of old did not discover the hidden retreat of lame- 

 ness ; but we have good reason to complain that veterinary colleges 

 did not find out the seat of a lameness which was acknowledged 

 by them as well as others to be in the foot. Had they cut into 

 the navicular joint in any case where death happened to befall the 

 lame horse, they could not have failed to have made the discovery; 

 and the readiest way of laying open the joint for inspection is to 

 make with a saw a vertical incision through the quarter of the hoof, 

 on either side, carrying the incisions obliquely inward through the 

 cartilages; then, with a scalpel detaching the perforans and per- 

 foratus tendons from their union with the contiguous parts, the 

 former may be dissected down to its place of insertion, and turned 

 back so as completely to expose the navicular (bursal) joint. 



The parts diseased, in cases of navicularthritis or grogginess, 

 are the under surface of the navicular bone and the upper one of 

 the perforans tendon. It will be remembered that the inferior or 

 posterior surface of the navicular bone is covered with cartilage 

 for the purpose of articulating, i. e. forming a bursa or joint with 

 the opposed tendon of the perforans muscle, which in the motions 

 of the bone, upward and downward, plays over it something after 

 the manner of a rope over a pulley : the surfaces of the bone and 

 tendon being in more complete co-aptation from the circumstance 

 of the bone having a transverse eminence (or crest) across its 

 middle, to which the tendon is fitted by a corresponding excavation 



