PERIODS OP OSSIFICATION. 9 



During the seventh month, in the astralagus. 



During the tenth month, in the cuboid bone and os hyoides. 



During the first year, in the coracoid process of the scapula ; first 

 piece of the coccyx, inferior turbinated bone, last piece of the sternum, 

 anterior arch of the atlas, os magnum, os unciforme, and external cunei- 

 form bone. 



During the third year, in the cuneiform of the carpus, internal 

 cuneiform, and patella. 



During the fourth year, in the middle cuneiform and scaphoid of the 

 tarsus. 



During the fifth year, in the trapezium and os semilunare. 



During the seventh year, in the second piece of the coccyx. 



During the eighth year, in the scaphoid of the carpus. 



During the ninth year, in the os trapezoides. 



During the twelfth year, in the os pisiforme and third piece of the 

 coccyx. 



During the eighteenth year, in the fourth piece of the coccyx. 



The ossicula auditiis are the only bones completely ossified at birth ; 

 the vertebrae are not completed until the five and twentieth year. 



The entire osseous framework of the body constitutes the skeleton, 

 which in the adult man is composed of two hundred and forty-six dis- 

 tinct bones. They may be thus arranged : 



Head 8 



Ossicula auditus 6 



Face 14 



Teeth 32 



Vertebral column, including sacrum and coccyx 26 

 Os hyoides, sternum, and ribs . . .26 

 Upper extremities ..... 64 



Lower extremities 62 



Sesamoid bones ..... 8 



246 



The skeleton is divisible into: 1. The vertebral column or central 

 axis. 2. The head and face, or superior development of the central 

 axis. 3. The hyoid arch. 4. The thoracic arch and upper ex- 

 tremities. 5. The pelvic arch and lower extremities. 



