(Pricked Foot - Nail-tread - Gathered Nail.)

Definition. - Under this heading we propose describing wounds of the foot occurring in the sole or in the frog, and penetrating the sensitive structures beneath.

Causes. - These we shall consider under two headings:

1. Wounds resulting from the animal himself 'picking-up' or 'treading' on the offending object.

2. Cases of pricking in the forge.

Those occurring under the first heading are, of course, purely accidental. In the majority of cases, the object picked up is a nail; but similar injury may result from the animal treading on sharp pieces of wood or iron, on pieces of umbrella wire, on pointed pieces of bones, broken-off stable-fork points, sharp pieces of flint, etc. The same accident may also occur in the forge as a result of the animal treading on the stumps of nails, from treading on an upturned shoe with the stumps of nails in situ, or from treading on an upturned toe-clip. It may also occur from an accidental prick with the stable-fork when 'bedding up,' or from casting part of a shoe when on the road and treading on the nails, in this case left sometimes partly in and partly out of the horn.

'Serious wounds of this description are also met with in animals engaged in carting timber from plantations in which brushwood has recently been cut down. This is, of course, from treading on the stake-like points that are left close to the ground. Hunters also meet with the same class of injury when passing through plantations or over hedge banks, where the hedge has just been laid low or cut down.

'Agricultural horses also meet with severe wounds of this class 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 the sole is rare.

Prick sustained at the hands of the smith may, of course, run in either of the following directions: (1) Directly into the position where the horny and sensitive laminae interleave; (2) between the sensitive laminae and the os pedis; (3) into the os pedis itself; (4) the nail may bend excessively immediately after entering the horn, and so pass either between the horny and sensitive sole; or (5) between the sensitive sole and the bone.

Classification. - Punctured wounds of the foot may be classified as follows:

Simple or superficial when penetrating no structure of great importance. For instance, a prick that penetrates to the sensitive sole and is not driven with sufficient force to seriously injure the os pedis we may regard as simple. In the same manner a prick to the frog that, although deep, is mainly concerned with penetrating the plantar cushion may also be classed as simple.

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.