174 THE SUPERIOR EXTREMITIES. 



cartilages, viz. : The body, not perfectly ossified ; and a bone on 

 each side of it, of a form almost rectangular, on which the oblique 

 processes are very distinguishable, and the transverse processes 

 may be ascertained. These bones are so applied to the body, 

 as to include a triangular space for the vertebral cavity. The 

 ends of the longest portions are nearly in contact behind ; but 

 the spinous process is not formed. The atlas is cartilaginous in 

 front, and has only the two late?al portions ossified. The verte- 

 bra dentata consists of four pieces ; for, in addition to the three 

 pieces common to the other vertebrae, the processus dentatus is a 

 distinct portion. 



The false vertebra, of which the sacrum consists, are each 

 formed of three bones as the true vertebras. 



The bones of the os coccygis are cartilaginous, except the 

 first, which is partly ossified. 



The ribs are almost perfect at birth : their heads and tuber- 

 cles covered with cartilage. The necessity of their motion in 

 respiration, immediately after birth, explains this difference be 

 tween them, and most of the other bones of the foetus. 



The sternum consists of several small bones, surrounded by 

 flat cartilages. Ossification goes on in these cartilages from 

 various points ; and the distinct bones finally unite into the three 

 pieces of which the sternum is finally composed. 



The ossa innominata, on each side, are formed of three dis- 

 tinct pieces, united at the acetabulum. 



The spine of the os ilium is cartilaginous ; and the lower part 

 of the bone is not completely ossified. 



The back part of the os ischium is ossified ; but the portion 

 which forms the acetabulum, the tuber, and the crus, is cartila- 

 ginous. 



The upper part of the os pubis, and that portion which forms 

 the symphysis, are ossified. The crus, like that of the ischium, 

 is cartilaginous. 



Of the Superior Extremities. 



Each superior extremity consists of the SHOULDER, the ARM, 

 the FOREARM, and the HAND. 



