OSTEOLOGY. 1 1 



THE VERTEBRAL COLUMN. 



The spinal column is composed of 52 segments, divided into 

 true and false. 



The true are divided into 7 cervical, 18 dorsal and 6 lumbar. 

 The false into the sacrum, of 5 segments closely fused, and the 

 coccyx, of from 15 to 18 segments more or less movable. 



Common Characteristics of Vertebrae. 



Each one has a body and an arch, enclosing the spinal canal, 

 which includes the spinal cord. The body has a superior face, 

 forming the lower boundary of the spinal canal, an inferior, two 

 lateral surfaces, a head, convex for articulation, an anterior extrem- 

 ity, and a concave posterior extremity. 



The arch projects upward from the top of the body, and con- 

 sists of pedicles, lamina, transverse, spinous and articular processes. 



The pedicles are two strong processes projecting upward and 

 supporting the transverse and articular processes. 



The transverse processes project laterally from the summit of 

 the pedicles. They are elongated antero-posteriorly in the cerv- 

 ical, short in the dorsal, and long in the lumbar regions. 



The lamina are two processes uniting above and forming the 

 spinous process; they enclose the spinal cord. 



The spinous processes project upward and backward, from the 

 junction of the laminae. They are small in the cervical, long in 

 the dorsal, rough and enlarged in the lumbar regions. 



The articular processes are four in number, two anterior and 

 two posterior. The former look upward, the latter downward. 

 In each is a notch, which, when in apposition, forms the interverte- 

 bral foramen. 



CERVICAL REGION. 



Common Characters. 



The body is long and thick and has an inferior spine. 



The spinous processes are a roughened line. 



The transverse or trachelian processes are elongated antero- 

 posteriorly and are in relation to the trachea. They are. traversed 

 at their base by a foramen, transmitting vessels, the vertebral. 

 The articular processes look downward and inward. 

 Peculiar Cervical Vertebrae. 



The ist or atlas articulates with the occipital, has a thin body, 



