166 
MANUAL OF MODERN FARRIERY. 
and above the heel of the coffin-bone, is placed a small 
bone, called the navicular bone. (See plate 6, fig. 10, e.) 
The use of this bone is to support and strengthen the union 
between the lower pastern and the coffin-bone, and to assist 
the flexor tendon in its action as it passes over it, in order 
to be inserted into the bottom of the coffin-bone, and forms 
a sort of joint with that tendon. The navicular bone is 
subjected to much pressure, as is also this tendon; and 
besides, there is much play between them in the bending 
and extension of the pasterns. 
Cause. —Like many other complaints of the horse, this 
is often induced by sudden and violent exercise after the 
animal has been allowed to stand in the stable inactive. 
The parts not being for some time adapted to overstrained 
action, there may be too much play between the bone and 
the tendon, and by concussion of the parts the periosteum 
or delicate membrane which covers the bones may be 
bruised ; or the cartilage of the bone may be inflamed, and 
thus produce destruction of it, and cause a lameness of 
the most painful description. From the navicular bone 
being so obscurely situated, it is difficult to ascertain by 
inspection when it is diseased. And this has puzzled many 
to find out the cause of lameness emanating from it, and 
has too often been attributed to the shoulder. Indeed 
the action of the horse with this lameness has all the 
appearance of being seated in the shoulder. Of late years 
the attention of veterinary colleges has been particularly 
directed to this point, and it has been found in numerous 
cases of dissection that this is the seat of this lameness, 
which has deceived and puzzled so many persons, both 
learned and unlearned. The membrane covering the bone 
has been found highly ulcerated, and the cartilage itself 
completely decomposed, and even the bones in a state of 
