212 DISEASES OF THE HORSE’S FOOT 
opening thus found should be carefully probed, and its 
depth and situation noted. 
At other times the prick is not so readily apparent. The 
nail or other object has penetrated and afterwards with- 
drawn itself. The natural elasticity of the horn, especially 
that of the frog, causes it to contract upon the puncture, 
and to largely obliterate the hole made. What, therefore, 
may look to be but a simple injury to the horn alone may 
in reality be the only evidence of a stab complicating the 
sensitive structures. It thus behoves the veterinary surgeon 
to follow up and earefully cut out any unnatural-looking 
mark in the horn, more especially if the horn is discoloured, 
or if blood is extravasated into its fibres, or there is moisture 
exuding from the part. 
In some cases of this description the knife in the act of 
paring comes into contact with the cause of the trouble. 
Sometimes this is a nail, sometimes a sharp and small 
piece of flint, so deeply penetrated as to have become quite 
buried. When met with in this manner, however, the 
foreign body is more often than not a splinter of wood 
deeply embedded in the cleft of the frog or in the frog 
itself. 
The fact that multiple punctures may occur should here 
be remembered, and the remainder of the inferior surface 
of the foot thinly pared. 
On withdrawal of the foreign object blood may immedi- 
ately follow. Should the former have been fixed in position 
for some time, however, pus is nearly always found at the 
bottom of the wound. As a rule, its removal is compara- 
tively easy, but one case recalls itself to the author’s mind 
in which the extraction was a matter of considerable diffi- 
culty. The offending object was a large, flat-headed nail, 
some 2 inches long. This was driven fast into the os 
pedis, and necessitated the employment of a pair of pincers 
and the exertion of some amount of force to move it from 
its position. 
In this connection it must be remembered that the pene- 
trating object sometimes breaks off after entering the foot. 
