Deep or penetrating when driven with sufficient force or in such a direction as to injure structures whose penetration is calculated to give rise either to serious constitutional disturbance or to permanent lameness.  In this category we may place injuries to the terminal portion of the perforans, puncture of the navicular bursa, fracture of the navicular bone and penetration of the pedal articulation, and splintering of the os pedis.

Symptoms and Diagnosis.—­While discussing the symptoms and diagnosis, we will still continue to consider our subject under the two headings of (1) accidental ‘gathering’ of some foreign body, and (2) pricks inflicted in the forge.

In a few cases belonging to the former class the veterinary surgeon is fortunate in obtaining a direct history of the injury.  The driver has seen the animal go suddenly lame, and has examined the foot for the cause.  Either the nail has been found embedded in the horn, or the puncture it has made detected, and the matter has been reported.  The foot is then explored and the full extent of the injury ascertained.

In many cases, however, it so happens that no evidence of the infliction of the injury is forthcoming.  The momentary lameness occurring at the time of the prick is unreported at the time by the attendant, and the horse for a time goes sound.  It is not until the changes set up by the subsequent inflammatory phenomena make their appearance, and lameness results, that attention is called to the foot.  When this happens there has, as a rule, been time for pus to form around the seat of puncture—­a matter of about forty-eight hours.

The horse is now brought out for the veterinary surgeon’s examination, going distinctly lame.  If the case is well marked there may then be noted by the man of experience many little signs pointing to the foot as the seat of the lameness.  These, though well enough known to the practitioner, are nevertheless difficult to describe.  It is, in fact, hard to say exactly in what they really consist, appearing to be as much a matter of intuition as of actual observation.

There is a peculiar ‘feeling’ characteristic in the gait.  The affected foot is put forward fearlessly enough, but is not nearly so rapidly put to the ground.  When at rest the foot is almost immediately pointed, and the pain at intervals manifested by pawing movements.  It is this extreme liberty of the rest of the limb, as evinced during the pawing movements, that really strikes one.  Shoulder, elbow, knee, and fetlock are all easily and painlessly flexed and extended.  There is nothing wrong with them; it must be the foot.  The short manipulation necessary to test the lameness—­viz., the walk and slow trot—­is sufficient to raise the animal’s pulse and quicken the breathing.