The Lower Extremity and Pelvis 187 



Ossification of tarsus : one centre for each bone except os calcis, which has an 

 epiphysis for its back part. The centre for astragalus and the main calcanean centre 

 appear during the sixth month and that for the cuboid about birth, so that it may or 

 may not present a nucleus at birth. The cuneiforms follow, the external first (one to 

 two), then the inner (two to three), and lastly the middle one (three to four). The 

 navicular commences to ossify about a year later. 



The epiphysial centre for the os calcis appears between eight and ten, and joins 

 the main bone about the age of twenty in males and about sixteen in females. 



There are occasionally separate small nuclei for the posterior tubercle of the 

 astragalus, and for the tuberosity of the scaphoid. 



Metatarsus : centres for the shaft eighth to tenth week, and epiphyses in the 

 third to eighth year, that for the first metatarsal appearing before the others. The 

 epiphysis for this bone is at the proximal end, while those of the remainder are distal : 

 occasionally there is also a proximal (styloid) epiphysis found on the fifth metatarsal. 



The epiphyses unite about twenty, those of women generally two or three years 

 earlier. 



Phalanges : these have proximal epiphyses. The shaft centres come first in the 

 last phalanges (end of second month), then in the first row (fourth to fifth month), 

 and lastly in the middle row, in which centres begin to appear in the fourth month 

 (second toe) and show slowly, that for the little toe not being generally present at 

 birth. Epiphyses appear about third to fourth year. 



The epiphyses join the shafts between sixteen and twenty, in women some years 

 earlier, the epiphyses of the first row being the first to join. 



The foot of the infant has certain characteristics of that of the ape. It is strongly 

 inverted, with the head of the astragalus directed more inwards and the neck longer 

 than in the adult : the first metatarsal is also somewhat directed inwards, with an 

 oblique articulation with the cuneiform, and is comparatively short. The extensor 

 muscles are apparently relatively short. As the foot comes into the adult position 

 these are lengthened, and the head of the astragalus comes to rest more on the susten- 

 taculum, while the outer (fibular) facet on the astragalus is increased in size. 



The anthropoid foot differs from that of man in the weaker development of the 

 great toe and its greater abduction and mobility, and also in the smaller size of the 

 tarsal components. The human embryonic foot shows at first marked abduction and 

 mobility of the toe, but this begins to be modified early in the third month, and the 

 modification slowly progresses into the earlier years of life. 



Many races show considerable mobility of the great toe, and in some low races 

 (e.g., the Veddahs) the great toe not only stands apart from the others, but the whole 

 tarsus is shorter and narrower, compared with the metatarsus, than in Europeans. 

 The relative and absolute length of the great toe is greater in men than in women. 



