SESAMOID BONES. 



179 



appearance in the following order : in the os calcis, at the sixth month of foetal life ; 

 in the astragalus, about the seventh month ; in the cuboid, at the ninth month , 

 external cuneiform, during the first year ; internal cuneiform, in the third year ; 

 middle cuneiform, in the fourth year. The epiphysis for the posterior tuberosity 

 of the os calcis appears at the tenth year, and unites with the rest of the bone 

 soon after puberty. 



Fig. 115. Plaoi of the Development of the Foot. 

 1 f is 



~ 2*- 



unites after pulerty 



.TW/fll' _ ~ ( 



Tarsus 



( C&ntre for to, 

 txcept Ox Calf it 



Metatarsus 



2 Centres far each tone 

 1 for Shaft 



1 far Digital Extremity 

 ezrccvt iff 



FJialangtt 



ZCentreifar each lione 

 IforSJiaft 



jlgpca. 6 y? 

 Unite. /6-ZO$ ij.: 



The Metatarsal bones are each developed by two centres: one for the shaft, and 

 one for the digital extremity, in the four outer metatarsal; one for the shaft, and 

 one for the base, in the metatarsal bone of the great toe. Ossification commences 

 in the centre of the shaft about the seventh week, and extends towards either 

 extremity, and in the digital epiphyses about the third year ; they become joined 

 between the eighteenth and twentieth years. 



The Phalanges are developed by two centres for each bone : one for the shaft, 

 and one for the metatarsal extremity. 



SESAMOID BONES. 



These are small rounded masses, cartilaginous in early life, osseous in the adult, 

 which are developed in those tendons which exert a certain amount of pressure 

 upon the parts over which they glide. It is said that they are more commonly 

 found in the male than in the female, and in persons of an active muscular habit 



