784 
DISEASES OF THE FOOT. 
present somewhat similar appearances, but are oftener of a grave 
character, affect to a greater degree the deep-seated tissues, produce 
at a later stage distortion of the hoof, and, worst of all, are apt to be 
followed by the formation of extensive exostoses and permanent lame¬ 
ness. Either the coronary band, the upper portion of the wall, or the 
skin is divided, and the injury often extends to subcutaneous structures, 
to the tendon of the extensor pedis, to the lateral cartilage, or even to 
the os pedis, and may even lay open the pedal-joint. The danger is 
increased by the fact of the wound being bruised and infected from the 
beginning, for which reason treads never heal by primary intention, and 
generally show a tendency to necrosis. The structure and position of 
the injured part favour this ; the tendons, the os pedis, and the lateral 
cartilage are readily destroyed, whilst necrosis is favoured by the sur¬ 
roundings of the coronary band, in which acute inflammatory swellings 
greatly interfere with nutrition, in consequence of the unyielding character 
of the horny wall. Finally, as treads most frequently occur during winter, 
the tissues are exposed to the action of cold and dirt, which are specially 
injurious. At this season of the year slight injuries to the coronet are 
readily followed by severe gangrenous processes, which show a strong 
tendency to extend to the sensitive laminae. Again, infection of the 
loose connective tissue lying under the coronary band often leads to 
diffuse cellulitis, which may extend to the pedal-joint, and give rise to 
incurable purulent inflammation. 
Luckily, healing is usually very complete at this point, and one 
sometimes sees cases where large portions of the coronary band have 
been destroyed, yet no defect remains in the formation of horn. This is 
rendered possible by the papillae of the coronary band and of the neigh¬ 
bouring skin replacing the lost parts. (On this point compare with Dollar 
and Wheatley’s “ Horse-shoeing and the Horse’s Foot,” pp. 104 et seq.) 
Destruction of a section of the coronary band is followed by cessation 
in the secretion of horn at that particular point. Acute inflammation 
of the band also interrupts the formation of horn, and produces a cavity 
in the horny wall, the width and length of which depend on the size of 
the region affected and on the time during which inflammation persists ; 
the longer the time, the greater the perpendicular measurement of the 
cavity ; the greater the extent of coronary band involved, the broader 
the resulting defect. When horn production is permanently checked, 
a depression forms in the wall, and gradually grows downwards until it 
extends from the coronet to the ground surface of the foot. To discover 
whether the horny wall will again recover its normal shape, the horn 
below the coronary hand must be inspected. 
A further obstacle to recovery consists in the papillae of the coronary 
band becoming thrust out of place, and not returning to their normal 
