142 DISEASES OF THE HORSE'S FOOT 



remember also that removal of the counter-pressure of the 

 frog with the ground tended to contraction of the wall's 

 solar edge when weight was applied. Connect these two 

 facts with the experience that this form of contraction more 

 often than not occurs in hoofs with sloping heels, and we 

 arrive at the following : 



1. The excessive slope of the heels tends to throw a more 

 than usual part of the body-weight upon the posterior 

 portion of the coronary margin of the wall, with a conse- 

 quent expansion of that part of the coronary margin 

 implicated. 



2. That the shoeing, in removing the counter-pressure 

 of the frog with the ground, is at the same time tending to 

 bring about contraction of the lower portions of the wall at 

 the heels and quarters. 



3. That this tendency to contraction will at first appear 

 in the thinner portion of the area of wall named — namely, 

 in that immediately below the bulging coronary margin. 



We thus get the appearance depicted in Fig. 79 — a con- 

 traction {a, a) of the heels in the horn below the coronary 

 margin, with the coronary margin itself bulging above, and 

 a hoof of apparently normal width below. 



We say ' apparently ' with a purpose, for, as actual 

 measurements will show, the wall near the solar edge is 

 really contracting, for reasons which we have just described 

 connected with shoeing. Its ' appearance ' of normal width 

 is accounted for thus : The contraction at a, a is caused by 

 the dragging inwards of the coronary cushion brought about 

 by the sinking downwards of the plantar cushion, with 

 which body it will be remembered the coronary cushion is 

 continuous. With the constant dragging in and down of 

 the coronary cushion there is given to the horn-secreting 

 papillae, studding both the lower third of its outer face and 

 its lowermost surface, a distinct ' cant ' outwards. Below 

 the lowermost limit of the coronary cushion, then, by reason 

 of the cant outwards of the coronary papilla in the 

 situations mentioned, the horn of the wall takes a more 

 outward direction than normal, a fact which lessens in 



