FAULTY CONFORMATION 121 



supply is lessened, their functions interfered with, and 

 side-bones result. 



Causes. — Upon the causation of contraction a very great 

 deal has been written, both by early veterinarians and by 

 those of the present, day. Many and widely differing 

 opinions have been advanced, but a careful resume of only 

 a few will lead one to certain fixed conclusions. 



We may consider the causes of contraction under two 

 headings — predisposing and exciting. 



Predisposixfi Causes of Contraction. — Among these we will 

 first mention heredity, although it is possible it should not 

 be deemed of so great account as it is by some. That the 

 shape of certain feet, especially those with low heels and 

 abnormally sloping walls, predisposes to contraction no one 

 will deny. So long, however, as the animal goes unshod, 

 so long does the foot maintain a normal condition of the 

 heels. In other words, it is not until the tendency to con- 

 traction already there is aggravated by careless shoeing and 

 the effects of work that it operates to any noticeable extent. 



The degree of contraction wall also be very largely 

 governed by the amount of the development of the frog. 

 With a frog of good size, low down, and taking part in the 

 pressure of the foot on the ground, contraction will be pre- 

 vented. On the other hand, an ill-developed frog, one 

 wasted by long-continued and spreading thrush, or one 

 robbed of its normal function by excessive paring in the 

 forge, is a common starting-point of the condition we are 

 considering. We have already referred to this in 

 Chapter III,, when considering the experiments of Lungwitz 

 in this connection. What we have to bear in mind in these 

 experiments is that the application of a pad to the frog, in 

 such a manner that effective ground-pressure is obtained, 

 results always in a marked expansion of the heels, and 

 that, with counter-pressure with the ground absent, ex- 

 pansion occurs to little or no extent. This is proof positive 

 of the enormous part the frog plays in maintaining an open 

 and elastic condition of the heels — a fact so insisted on by 

 Coleman. 



