CHANGES IN FORM OF THE HOOF. 115 



especially the cartilaginous plate at the back of the pastern 

 (fig. 27, e), become excessively tense, causing the navicular bone 

 to be applied closely to the posterior part of the articular 

 surface of the coronet bone, and the anterior rounded part of 

 its articular prominence to be pressed firmly into the articular 

 depression of the pedal bone. The formation of the articular 

 groove of the coronet bone favours the fixation of the pedal joint 

 at the moment when the parts are relieved of weight. When 

 flexion is complete, extension immediately begins, and the hoof 

 is advanced, whereupon the stage of weight-bearing commences 

 and is followed by relaxation, a series of changes which recurs 

 again at each step. 



In order to ensure free and perfect action, it is absolutely 

 necessary that the hoof should leave the ground lightly and 

 easily. Everything which impedes this phase of movement 

 interferes with action, and may lead to disease of tendon, 

 ligament, or bone. Such action can, however, only result 

 when weight is equally distributed throughout the joints of 

 all four limbs, and the (imaginary) axis of the foot, as viewed 

 from the side, appears nearly straight. Slight deviation of 



the axis of the foot in a forward direction, thus I does no 



harm, but deviation backwards is excessively injurious, be- 

 cause it leads to greater weight being thrown on the above- 

 mentioned ligaments, and may produce lameness without 

 the horse being exposed to any special strain. Injury may 

 result even when standing in the stable, especially when the 

 surface of the pavement falls too much towards the heel-post. 



Bearing in mind these facts, the farrier should strive to so 

 form the hoof that the load between the ligaments and tendons 

 in the region of the pedal joint is evenly distributed. 



Changes in Form of the Hoof. 



We have seen that the body>weight is conveyed to the pedal 

 bone through the medium of the coronet bone. As, however, 

 the pedal bone is connected through the laminal sheath of the 

 sensitive wall with the horny wall, it is clear that the weight 

 is further conveyed to the horny wall itself. This, like the 

 other parts of the hoof, is somewhat elastic. Elastic bodies 

 change their shape under pressure, a rule to which the hoof 



