Complications. - The first complication likely to arise in a case of sand-crack is that attending simple laceration of the sensitive structures in a deep lesion. With the laceration all the phenomena of a repairing inflammation make their appearance. As a result, there is more or less heat according to the degree of inflammatory hyperaemia, swelling according to the amount of inflammatory exudate, and pain according to the amount of pressure the two foregoing bring to bear on the nerves in the inflamed area.

A second and more serious complication is the greater inflammation set up by the introduction into the crack of foreign substances. Small portions of gravel and flint, both by the irritation set up by their friction and by the infection they carry in with the dirt surrounding them, are responsible for the mischief.

When, from direct communication with the blood-stream, due to extensive haemorrhage, bacteria from the outside gain entrance, this simple inflammation is further complicated by the formation of pus, or a limited gangrene of the keratogenous membrane.

In cases of great severity the gangrene of the keratogenous membrane spreads until the deeper structures are involved. We then get a necrosis (in the case of toe-crack) of the extensor pedis, and sometimes caries of the os pedis.

In like manner the necrotic changes occurring under these circumstances may invade the deeper structures in the region of quarter-crack. As a result of this, we may have the starting-point of suppurating corn, or necrosis of the lateral cartilage - in other words, cartilaginous quittor.

Commonly accompanying quarter-crack is the condition of contracted heels and atrophied frog. Sometimes described as a complication of sand-crack, it appears to us more rational to rather regard the sand-crack as a result or complication of the vice of contraction.

The overlapping of the edges of the crack before referred to occasionally gives rise to the condition known as false quittor. A probe or a director passed beneath the overhanging ledge of horn reveals sometimes a fissure of 1 inch or considerably more in depth, and quittor is diagnosed. A careful paring away of the overhanging horn, however, reveals the true state of affairs, and exposes to view the original cause of the mischief - a simple fissure in the wall.

A serious complication - one fortunately met with but rarely - is that of keraphyllocele. This is a tumour-like growth of horn, varying in size from the thickness of an ordinary quill pen to that of one's middle finger, growing down from the coronary cushion, and attached to the inner side of the wall of the hoof. With this lameness is always present, and more or less deformity of the hoof results. This condition will be found described at greater length in Chapter IX (Inflammatory Affections Of The Keratogenous Apparatus. A. Acute Laminitis).

Prognosis. - In the case of sand-crack this should always be guarded. It may be taken as a general rule that cracks commencing from the coronary margin are more troublesome to deal with than those originating below. The reason is not far to seek. They here affect the wall just where the bevel in it for the accommodation of the coronary cushion has rendered it weakest. Not only is it weakest, but being more resilient than the portions below it, it suffers more from the alternate movements of expansion and contraction of the foot than does the horn below.

Although in many cases a cure of the existing crack may be easily accomplished, regard should be paid to the possibility of its recurrence, either in the same position or elsewhere. Really, in offering an opinion as to the future usefulness of an animal so affected, a greater attention should be directed to the animal's conformation than to the crack itself. Where the vice of conformation giving rise to it (as, for example, contracted heels or upright hoof) gives hope of being remedied, then naturally it may be safely said that the liability to sand-crack goes with it.

A like favourable prognosis may be given in the case of cracks occasioned by purely accidental causes.

Ordinarily, however, cracks once commenced tend rather to increase than decrease in size and severity. From being superficial and incomplete, they become complete and deep, with every unfavourable circumstance that an increase in size and depth brings with it.

This much, however, may be promised to the owner. A simple crack, even though originating from the coronary margin, is, in the vast majority of cases, curable. Under a rational treatment its increase in size may be prevented, and a sound wall caused to grow down from the coronet.