The tarsal. bones are each ossified from a single center, excepting the calcaneus, which has an epiphysis for its posterior aspect. The centers make their appearance as follows : in the calcaneus, at the sixth month of fetal life in the talus, about the seventh month ; in the cuboid at the ninth month: in the lateral cuneiform; during the first year ; in the medial cuneiform, during the third year ; in the intermediate cuneiform and navicular, during the fourth year. The epiphysis for the posterior surface of the calcaneus begins to ossify between the sixth and tenth years; and unites with the rest of the bone soon after puberty. The posterior tubercle of the talus is sometimes ossified from an independent center; and may remain connected to the rest of the bone by cartilage. It is then named the ostrigonum.
The phalanges are each ossified from two centers : a primary one for the shaft and an epiphysis for the base. The primary centers for the distal phalanges appear about the eighth week of fetal life : those for the proximal phalange between the twelfth and sixteenth weeks, and those for the intermediate phalanges after the sixteenth week (that for the phalanx of the fifth toe does not usually appear until after birth). The epiphyseal centers appear between the third and sixth years and unite with the shafts about the seventeenth or eighteenth year.
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