<P> A stone bruise affects the sole of the horse's foot . It is often caused by a horse treading on a stone or sharp type of object, landings from high jumps and excessive exposure to snow . A major symptom is lameness . </P> <P> Bars are the inward folds of the wall, originating from the heels at an abrupt angle . The strong structure built up by the extremity of the heel and of the bar is named the' heel buttress' . The sole between the heel walls and the bars is named the' seat of corn', and it is a very important landmark used by natural hoof trimmers to evaluate the correct heel height . The bars have a three - layer structure, just like the walls (see above). When overgrown, they bend outwards and cover the lower surface of the sole . </P> <P> The third phalanx (coffin bone; pedal bone; P3;) is completely (or almost completely) covered by the hoof capsule . It has a crescent shape and a lower cup - like concavity . Its external surface mirrors the wall's shape . The corium, a dermo - epidermal, highly vascularized layer between the wall and the coffin bone, has a parallel, laminar shape, and is named the laminae . Laminar connection has a key role in the strength and the health of the hoof . Beneath the rear part of the sole, there is the digital cushion, which separates the frog and the bulb from underlying tendons, joints and bones, providing cushioning protection . In foals and yearlings, the digital cushion is composed of fibro - fatty, soft tissue . In the adult horse, it hardens into a fibrocartilaginous tissue when sufficient, consistent concussion stimulates the back of the hoof . Normal transformation of the digital cushion into fibrocartilagineous tissue is now considered a key goal, both for prevention of, and for rehabilitation of recovering cases of navicular syndrome . The flexor tendon lays deeper, just along the posterior surface of the small pastern bone (PII) and navicular bone, and it connects with posterior surface of P3; the navicular functions as a pulley . </P> <P> The horse hoof is not at all a rigid structure . It is elastic and flexible . Just squeezing the heels by hand will demonstrate that . When loaded, the hoof physiologically changes its shape . In part, this is a result of solar concavity, which has a variable depth, in the region of 1--1.5 cm . In part, it is a result of the arched shape of the lateral lower profile of the walls and sole, so that when an unloaded hoof touches a firm ground surface, there is only contact at toe and heels (active contact). A loaded hoof has a much greater area of ground contact (passive contact), covering the lower wall edge, most of the sole, bars and frog . Active contact areas can be seen as slightly protruding spots in the walls and in the callused sole . </P>

What's the purpose of the soft rubbery sole found on a newborn foal's hoof
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