126 
NAVICUL ARTHRITIS. 
Fourthly. — The too many instances we meet with in practice of 
the obstinate lameness remaining after we have removed the con- 
traction. Many are the instances of groggy horses with con- 
tracted hoofs, that after having been at grass for a considerable 
time, perhaps for a whole year, whose feet have so altered as to 
have become circular, and every purpose answered except the 
principal one, the removal of the lameness. 
Fifthly. — The sudden manner in which they are frequently at- 
tacked with this disease. Horses that were known never to have 
been lame have become violently lame on the road, suddenly, with 
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 
