THE METATAKSUS. 



265 



tarsus determines the side-to-side roundness of the instep, whilst its plantar surface 

 forms arches in both a transverse and a longitudinal direction, in which the softer 

 tissues of the sole are lodged, and so protected from injury. 



Ossification. Unlike the carpus, the tarsus is at birth partially ossified. At this 

 period there is a well-marked osseous nucleus within the body and neck of the talus, 

 and the calcaneus is extensively ossified. In the latter the deposition of earthy matter 

 appears as early as the sixth month of foetal life, whilst in the talus the ossific centre 

 makes its appearance in the later weeks of gestation. Shortly before or after birth the 



FIG. 271. RADIOGRAPH OF THE HAND 

 AT BIRTH. 



It will be noticed that whilst the primary 

 centres for the metacarpus and phalanges 

 are well ossified, the carpus is still 

 entirely cartilaginous. 



FIG. 272. RADIOGRAPH OF THE FOOT 

 AT BIRTH. 



The centres of ossification for the calcaneus 

 and talus are well developed, the nucleus for 

 the cuboid is quite distinct, and in this instance 

 the third cuneiform is already commencing 

 to ossify. 



2. 



cuboid begins to ossify, succeeded early in the first year by the third cuneiform, followed 

 in order by the second cuneiform, first cuneiform, and navicular. The ossific centre 

 the latter appears at the third year or somewhat later. An epiphysis, which forms a 

 p over the extremity of the tuberosity of the calcaneus, appears from the seventh to the 

 ninth year, and fusion is completed between the ages of sixteen and twenty. 



To emphasize the different conditions which obtain in the wrist and ankle, at, and for 

 me time after birth, drawings of radiographs of both are given. 



The Metatarsus. 



The metatarsal bones, five in number, in their general configuration resemble the 

 metacarpal bones. They are, however, slightly longer, their bases are proportionately 

 larger, their bodies are more slender and are compressed from side to side, and their 

 heads are proportionately smaller. They are named numerically the first, second, 

 third, fourth, and fifth metatarsal bones, in order from the tibial to the fibular side. 

 The first can be readily recognised on account of its stoutness; it is also the 

 shortest of the series. The second is the longest of the five, and the fifth can 

 easily be distinguished by the projecting tubercle at its base. 



