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 hemorrhage. 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 
horn, 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, 
