TREADS AND 1N.JTKIKS TO TIIK COBONET. 1059 



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 sloughing 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. 



Destruction of a section of the coronary hand 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 perpen- 

 dicular measurement of the cavity ; the greater 1 he 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 

 band 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 

 position. During acute inflammation the papillae of the coronary 

 band are displaced relatively to one another, and must regain their 

 former position before they can again produce a normal growth of 

 horn. This is effected by the neighbouring papillae, which have not 

 suffered displacement. As the growth of horn starts from the 

 periphery of the injury, the diseased and displaced papilla? are gradually 

 brought into position by the growth of neighbouring horn tubules ; 

 and as repair proceeds, the normal state is restored. Sometimes 

 the growth of horn is irregular, because it sets in before swelling has 

 completely disappeared, and the papillae are unable to take up their 

 normal position ; or, again, horn production does not proceed 

 regularly from the periphery towards the centre of the injury. The 

 displaced papillae then become fixed in their abnormal position, 

 and produce a horny prominence on the coronet, in consequence of 

 certain of them not contributing to the formation of the wall, but 

 producing independent masses of horn. The horny wall then shows 

 a defect at the point in question, which detracts from its solidity. 

 Sometimes the exterior of the wall is thickened, because horn formation 



