ANATOMY OF VERTEBRATES. 



23 



right angles in tliolr course to the vascular canal, with which they 

 communicate ; and tlicy form the U 



essential vehicle of the material 

 for future trrowth. 



H4f 



§ 12. Growth of hone. — In 

 fishes the l^oncs continue to grow 

 throughout life, and their peri- 

 phery, whether in the flat Irenes of 

 the head which overlap each other, 

 or in the thicker bones that inter- Thof<,ni 

 lock, is cartilaginous or membranous, 

 sive ossification. The long bones of most reptiles retain a layer 

 of ossifying cartihrge beneath the terminal articular cartilage ; 

 and growth continues at their extremities while life endures. 



15 



^ usbiuuca l>y the boiic-cells 



and the seat of 



progres- 





.' 1 





_'. ^ 



..-■f<k\r..-t-~-. 







-c* J 







■«i' 



ctiou from the de!i?c portlDii ol tin 



Some of the long bones in frogs, birds, and most of those in mam- 

 mals, have their ends distinct from the body or shaft of the grow- 

 ino- bone; these separately ossified ends are termed 'epiphyses': 

 the seat of the active growth of the sliaft is in a cartilaginous 

 crust at the ends supporting the epiphyses. When these coalesce 

 Avith tlie shaft, growth in the direction of the Ijone's axis comes to 



