6 4 



CARTILAGE AND BONE 



first supposed. In ontogeny it is the latest to appear ; it is formed 

 chiefly in the region of the epiphyses, and is almost entirely of a 

 purely provisional character. By far the greatest bulk of the endo- 



.-"*'* * <?, 



j?< s> s> . * <s 



-S^^^sS >/*/, 



^> ^3^03 G 



^2<&iM 



^c\ ^-v'. 



" 



10 



FIG. 43. 



Enlarged view of a portion of a section through the phalanx of a mammalian foetus showing 

 the development of bone (from a preparation lent by Dr. G. Mann). 1, hyaline cartilage matrix'; 

 2, cartilage cell ; 3 and 4, the same becoming modified near the region of ossification ; 5, calci- 

 fied cartilage matrix ; 6, blood-vessels invading the cartilage ; 7, osteoblasts depositing bone ; 

 S, island of cartilage, remains of matrix surrounded by newly-deposited bone ; 9, endochondral 

 bone substituted for cartilage ; 10, perichondral bone deposited outside ; 11, bone-cell ; 1'2, 

 invading cells destroying cartilage. 



skeleton is of the second or sub-pcriosteal variety. This is the first 

 bone to appear in the ossification of the limb-bones, for instance, 

 and is deposited layer upon layer by the osteoblasts lining the 



