MR. Turner's original communication. 137 



this complaint, and never after become sound again to work, and 

 the owner or groom shall not have had the least suspicion that the 

 animal was becoming lame. If contraction were the cause, surely 

 the lameness would, in every instance, take place gradually. 



These points induced me to search for another cause for the 

 lameness. By dissection, I have discovered another ; and, to the 

 best of my knowledge, it is a disease which has never been 

 described by any author. The seat of it is in the navicular joint 

 of the foot : I mean the joint formed by the navicular bone and 

 the flexor tendon, where the tendon slides over the navicular bone ; 

 the circumscribed cavity which is supplied with synovia or joint 

 oil, to prevent friction between the internal polished surface of the 

 tendon and the smooth cartilage covering the navicular bone. The 

 worst stage of the complaint is a total destruction of the navicular 

 joint, which is so completely disorganized, that it can no longer 

 act as a joint ; there is not a drop of synovia to be found in it. 

 The cartilage covering the navicular bone next the tendon is either 

 entirely absorbed, or else in a complete state of ulceration : the 

 corresponding surface of the flexor tendon, which was before as 

 smooth as the highest polish, has now become rough, and the deli- 

 cate membrane lining it, abraded; and in most of the desperate 

 cases there is a strong adhesion of the tendon to the navicular 

 bone. When adhesion is present, there is, generally, besides the 

 loss of cartilage, a loss also of part of the navicular bone itself, 

 a small hole formed in its centre from absorption. In some in- 

 stances there is an ossification of the parts contiguous, but I have 

 dissected many desperate cases of this navicular disease without 

 any ossification. When the disease is less violent, there is a defi- 

 ciency of synovia and an inflammation of the secreting membrane ; 

 an absorption of part of the cartilage of the navicular more parti- 

 cularly in the centre, and some roughness of the corresponding 

 surface of the tendon : in this milder form of the complaint there 

 is no adhesion of the tendon to the bone. 



I have dissected every groggy foot that I have been able to pro- 

 cure : in every instance, without one exception, I have found the 

 navicular joint diseased. I have found it in groggy feet with con- 

 traction, and also to the same extent in good-looking open feet. 



VOL. IV. T 



