STRUCTURE AND DISEASE OE THE NAVICULAR CONE. 287 
aud that these are perhaps more complicated in their liga- 
mentous arrangements than some of the other joints of the 
member, 
The chief articulation is formed by the lower end of the 
coronary bone, and the double concavity into which it fits, 
and which is constituted by the union of the pedal and 
navicular bones, their cartilage-covered upper faces offering 
a wide surface for contact and interplay with that bone. The 
second articulation is between the pedal and navicular bones, 
at the points already indicated, and which are also covered 
by true articular cartilage. 
The three bones are maintained in apposition by four 
fibrous bands — two on each side — designated the anterior 
and posterior lateral ligaments, and a single or interosseous 
ligament that attaches the navicular to the pedal bone. 
{To he continued .) 
ON THE STRUCTURE AND DISEASE OF THE 
NAVICULAR BONE, 
By T. D. Broad, M.R.C.V.S., Bath. 
By your permission I will make a few remarks on Mr. 
Fleming's paper in last month's Veterinarian , as I presume 
he refers to my views on navicular disease. When speaking 
of the anatomy and pathology of the navicular bone (at page 
184), Mr. Fleming states that “ there is enclosed in the 
navicular bone a nucleus of a loose or spongy texture." 
Now, a longitudinal section of the bone will show that, with 
the exception of the outer shell, “ which is not thick," the 
whole substance of the bone is of a sponge-like texture. He 
next states that the inferior face of the bone is covered by 
a particular membrane, which is not articular cartilage, but 
a membrane which differs but little (if anything) from those 
membranes which are usually classed by the name of stra- 
tified fibrous cartilages, and cover bony prominences or 
grooves, over or through which tendons glide. I have 
thoroughly examined the cartilage microscopically on each 
surface of the navicular bone. Generally a few fibres inter- 
spersed in the substance of cartilage are to be detected on 
the inferior surface, but not sufficient to constitute it fibro- 
cartilage, such as exists between the vertebrae, the interarti- 
cular discs on the tibia, maxillary margin of the acetabulum, 
and other joints. 
When tendons run through sheaths they are always 
