366 SOLUTIONS OF CONTINUITY IN THE HORN. 



The depth of the crack may be measured with a nail beateo 

 flat at the point. Some sandcracks are ' open,' others are 

 ' closed ' or only slightly open. 



The causes comprise : injuries destroying a portion of the 

 coronary band and thus leading to changes in the character of 

 the wall ; excessive tension at the coronary margin in upright 

 feet (producing sandcrack of the toe) and in flat and con- 

 tracted hoofs (sandcrack of the quarter). Fissuring is favoured 

 by weakness of the wall, drying of the horn, bad fitting of the 

 shoe, ' springing ' the heels when shoeing with ordinary shoes, 

 in the case of carriage horses by trotting work on hard, rough, 

 or frozen streets, and in riding horses by trotting, galloping, or 

 jumping with a heavy rider. Sandcracks sometimes start 

 from the bearing margin, as when horses are turned out without 

 shoes and without the hoofs having been rounded off; when 

 the bearing surface of the shoe is uneven, and when the 

 counter-sinks allow the nails to penetrate too far or when the 

 nails themselves are too large. 



Prognosis. — Sandcracks vary in gravity according to their 

 cause and position. The most troublesome, perhaps, are those 

 resulting from excessive strain on the coronary margin produced 

 by unequal distribution of weight, because recovery then 

 depends upon the downward growth of an unbroken mass of horn 

 from the coronary band, and this again depends upon the length 

 of the crack. The animal may be useless for months, for a 

 time, in fact, sufficient for the hoof to be entirely renewed. 

 During this period fresh cracks may develop if attempts are 

 made to use the horse for trotting, galloping, or jumping, and 

 again postpone recovery or seriously imperil it. Cracks result- 

 ing from wounds of the coronary band are also grave, especially 

 when a portion of the horn-secreting structure is destroyed. 

 On the other hand, those due to drying of the horn or to bad 

 shoeing are unimportant, provided the hoofs are well-shaped 

 and sound. The same is true of cracks at the bearing surface. 



Treatment. — Eecovery is assisted by fixing the opposing 

 margins of the crack firmly in position, thus preventing the 

 new horn from being torn through. Immobilisation of the 

 edges is not, however, the principal point, and it is much more 

 important to attend to the distribution of weight in the hoof 

 and to improvement of its form. 



