04 THE NAVICULAR DISEASE, OR CHRONIC 
The advanced stage of the complaint is a total destruction of 
the joint, and which is so completely disorganised, 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 ulcera¬ 
tion; and the corresponding surface of the flexor tendon, which 
was before as smooth as the highest polish, has now become 
rough, and the delicate and sensitive membrane lining it abraded; 
and in most cases of long duration there is a strong adhesion of 
the tendon to the navicular bone. When this adhesion, or mor¬ 
bid insertion of the tendon into the bone, is present, there is ge¬ 
nerally, exclusively of the loss of cartilage, a diminution also of 
the navicular bone itself, leaving a hole in its centre formed by 
absorption. 
In the earlier stage of the disease, there is a deficiency of sy¬ 
novia, but not a total absence of it; the secreting or synovial 
membranes highly inflamed; an absorption of part of the carti¬ 
lage of the inferior surface of the navicular bone, more particularly 
in the centre; and a roughness of the corresponding surface of 
the tendon. At this crisis of the complaint there is only a slight 
adhesion of the tendon to the bone. 
In very recent cases I have not found the tendon adhering to 
the bone, but I have invariably perceived a lesion or abrasion of 
a small portion of synovial membrane from the tendon, and gene¬ 
rally that part of it which is opposed to the centre of the bone, 
exhibiting small streaks in the tendon ; whilst the cartilage cover¬ 
ing the corresponding part of the bone has appeared discoloured. 
In the inactive state of the horse, the limbs have no other weight 
to sustain than the mere gravity of the superincumbent matter, 
each limb supporting only a share of the burthen; but when the 
animal is in motion, not only is the pressure of the superincum¬ 
bent weight increased, but the entire weight of the fore quarters, 
with the head and neck, being alternately conveyed to each fore 
foot separately, a more favourable impression is made by the weight, 
and the partial contraction prevented. 
This disease more especially attacks that very foot which we 
are in the habit of calling a strong one, where the fibres of the 
horn are firm and tough, the toe thick and round, the wall or 
quarters strong, and high at the heels; the bars strong and deeply 
buried in the foot; the sole thick and concave. Such a foot is 
not so much disposed to approximation of the heel as it is to the 
occult or partial contraction. 
A slight stricture is observable round the middle of the crust, 
or towards the upper part. When this is not present, there is 
invariably an indentation or slight falling in of one quarter, gene- 
