208 



TEXT-BOOK OF EMBRYOLOGY. 



ter appears and finally fuses with the corresponding bone about the twenty- 

 fourth year. 



The femur, tibia andfibula are preformed in cartilage. In the femur a center 

 of ossification appears about the end of the sixth week and gives rise to the 

 shaft; similar centers appear in the tibia and fibula during the seventh and 

 eighth week, respectively. In the femur a distal epiphyseal center appears 

 shortly before birth, and during the first year after birth a proximal center 

 appears for the head. These centers do not unite with the shaft until the individ- 

 ual ceases to grow. The great and lesser trochanters also have accessory ossifica- 

 tion centers. In the tibia the center of ossification for the proximal epiphysis 

 appears about the time of birth, the one for the distal during the second year. In 



Fibula 



Calcaneus 



Tibia 



Cuboid -- 

 Cuneiform III 



Metatarsals -'- 

 FIG. 187. Diagram of cartilages of left leg and foot of human embryo of 17 mm. Ha gen. 



the fibula the epiphyseal centers appear during the second and sixth years after 

 birth. The cartilage of the patella appears during the third or fourth month 

 of foetal life, and ossification begins two or three years after birth. 



The bones of the tarsus, like those of the carpus, are preformed in pieces of 

 cartilage which are arranged in two transverse rows. The proximal row con- 

 sists of three pieces, one at the end of the tibia (tibial), one at the end of the 

 fibula (fibular), and the third between the two (intermedial). At an early stage 

 the tibial and intermedial fuse to form a single piece of cartilage which corre- 

 sponds to the talus (astragalus) bone. The fibular cartilage corresponds to the 

 calcaneus (os calcis). The distal row is composed of four pieces of cartilage 

 which correspond to the first cuneiform (internal), second cuneiform (middle), 

 third cuneiform (external), and cuboid (Fig. 187). Between the two rows is a 



