lass from
treading on an upturned harrow.'[A]

[Footnote A: _Journal of Comparative Pathology and Therapeutics_, vol. iv.,
p. 2.]

It has been remarked how strange it is that nails should so readily
penetrate the comparatively hard covering of the foot. The matter, however,
admits of explanation. One knows from common observation how easy it is to
tilt a nail with its point upwards by exerting a pressure in a more or less
slanting direction upon its head. This is exactly the form of pressure that
is no doubt put upon the nail if the animal treads upon it when moving at
any pace out of a walk. The foot in its movement forward tilts the nail
up, and almost simultaneously puts weight upon it. The great weight of the
animal is then quite sufficient to account for its ready penetration.

In purely country districts cases of punctured foot are of far less
frequent occurrence than in large towns. In the latter, animals labouring
in yards where a quantity of packing is done, or engaged in carting
refuse containing such objects as we have mentioned, or broken pieces of
earthenware or glass bottles, meet with it constantly.

For the manner of causation of those wounds to the foot occurring in
the forge the reader may be referred to the matter under the heading of
'nail-bound.' As in that case so in this the nail may be wrongly directed
by improper fitting of the shoe, by the 'pitch' of the hole, or by the
position of the hole. The nails may also be wrongly directed as a result of
faulty pointing, or by meeting with the stump of a nail that has carelessly
been allowed to remain in the substance of the horn.

Often pricking is a result of carelessness engendered by a rush of work.
Often it is almost unavoidable on account of the character of the foot that
is brought to be shod. Feet with thin horn, especially a thin sole, feet
with horn shelly and brittle, each in their way are difficult to shoe.

Sometimes pricking is purely accidental, as in the case of a 'split' nail.
The nail as it is driven splits at its point, and continues to split down
its centre, one half emerging at the correct spot on the wall, the other
half bending inwards, and penetrating the sensitive structures.

_Common Situations of the Wound_.--In a case of picked-up nail the common
seat of puncture is about the point of the frog, either in one of the
lateral lacunae, in the median lacuna, or the apex of the frog itself. In
comparison with this puncture of