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The heel proper in digitigrades and ungulates is raised off the ground and is commonly known as the “knee” or “hock,” while the term “heel” is applied to the hind hoofs.

The horse is eminently “digitigrade,” standing on the extremity of the single digit of each foot, which is kept habitually in a position approaching to vertical.

It is necessary among the ruminants to make an exception of the camel and the llama, which are digitigrades.

The thoracic vertebrae number 13; the feet are digitigrade, with five front and four hind toes, of which the claws are retractile; and the metatarsus is haired all round.

But the digitigrade modification necessitated a change of structural plan, to the extent of raising the wrist and ankle joints off the ground, so as to make the quadruped walk on its fingers and toes.