DISEASES FROM FAULTY CONFORMATION 167 



the wall of the heels thus brought about leads to a pro- 

 portionate contraction of the wall at the toe, especially at 

 the edges of the crack, thus causing undue pressure upon 

 the exact spot of the wound in the sensitive structures. 

 Ascending — the weight in this case transferred from the 

 posterior to the anterior portion of the foot — the expansion 

 of the heels becomes a contraction, with a corresponding 

 lessening of the contraction at the toe and a distinct 

 decrease in the lameness. 



In the case of a deep but recent crack there is always 

 more or less haemorrhage. This favours risk of infection 

 of the lesion with pus-forming organisms, and so leads to a 

 more or less pronounced lameness, a degree of swelling, 

 heat and tenderness in the coronet above, and a certain 

 amount of surgical fever. 



The acute symptoms subdued, but the fissure still remain- 

 ing, gives us the crack we have classified as ' old.' This 

 may in every case be distinguished from a more recent 

 lesion by the amount of thickening of the overhanging 

 coronet, and the presence of an increased quantity of sub- 

 coronary horn in the region immediately about the crack. 

 The previous inflammatory changes in the adjoining sensi- 

 tive structures have here led to an increased secretion of 

 lorn, and a greater or less deposition of inflammatory con- 

 nective tissue in the wounded coronary cushion. 



Sand-crack of the toe always follows the direction of the 

 horn fibres. That of the quarter, however, may on occasion 

 run a course that is somewhat zigzag, first following the 

 direction of the horn fibres for a short distance, then 

 travelling in a horizontal direction, and finally continuing 

 its course again in a line with the horn fibres, commonly 

 at a point posterior to that at which it commenced. 



In a quarter-crack that is old, and when contraction of 

 the heels exists (which in this case it usually does), then 

 will often be found overlapping of the edges of the crack. 

 The expansion of the wall brought about when the body- 

 weight is on the heels, cannot, by reason of the break in it, 

 continue itself anterior to the crack. As a consequence. 



