22 UEVELOPEMENT OF BONE. 



From the sixth to the eighth week, ossification commences first 

 in the clavicle, then in the lower jaw, upper jaw, and femur. 



From the eighth to the tenth week, in the frontal, occipital, 

 humerus, radius and ulna, tibia and fibula, scapulas, ribs. 



From the tenth to .the twelfth week, in the temporal, sphenoid, 

 malar, parietal, palate, nasal, vertebra, metacarpus, metatarsus, last 

 phalanges of the hands, and feet. 



From the third to the fourth month, in the vomer, first and second 

 phalanges, ossa innominata. 



From the fourth to the fifth month, in the ethmoid, lachrymal and 

 spongy bones. 



From the fifth to the sixth month, in the sternum, carpus, and 

 tarsus. 



From the sixth to the tenth month in the os hyoides, coccyx, and 

 cuboid bone. 



At one year, in the coracoid process of the scapula, os magnum, 

 os unciforme, and internal cuneiform bone. 



At three years, in the patella, and carpal cuneiform bone. 



At four years, in the external and middle cuneiform bone. 



At five years, in the tarsal scaphoid bone, trapezium, and semi- 

 lunare. 



At eight years, in the carpal scaphoid. ^N^ 



At nine, in the trapezoid, and at the twelfth year, in the pisiform" 

 bone. 



The ossicula auditus are the only bones completely ossified at 

 birth. 



The entire osseous framework of the body constitutes the skeleton, 

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

 distinct bones. They may be thus arranged : 



Cranium ....... 8 



Ossicula auditus 6* 



Face 14 



Teeth * . 32 



Vertebral column 24 



Os hyoides, sternum, and ribs ... 26 

 Upper extremities . . . . .64 



Pelvis 4 



Lower extremities 60 



Sesamoid bones 8 



246 



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

 axis. 2. The cranium and face or superior developement of the 

 central axis. 3. The hyoid arch. 4. The thoracic arch and upper 

 extremities. 5. The pelvic arch and lower extremities. 



* Wilson describes three bones to the ear viz : malleus, incus and stapes, making- the 

 orbiculare of other anatomists a part of the stapes. He also counts thirty-two teetli 

 in this enumeration, which is not common. G. 



