OSTEOLOGY. 1 1 



THE VERIEBRAL COLUMN. 



The spinal column is composed of 52 segments, divided into 

 true ^ViA 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 spifial canal, 

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

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

 lateral surfaces, a head, convex for articulation, an antejior ex- 

 tremity, and a concave posterior exirejuity. 



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

 sists of pedicles, lamince, transverse, spinous and articular pro- 

 cesses. 



The pedicles are two strong processes projecting upward and 

 supj)orting the transverse and articular processes. 



The t?'a?isverse processes project laterally from the summit of the 

 pedicles. They are elongated antero-posteriorly in the cervical, 

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



The lamince are two processes uniting above and forming the 

 spinous process ; they enclose the spinal cord. 



The spi7ious 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 Ime. 



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 ?cci'^ inward. 



Peculiar Cervical Vertebrae. 



The 1st or atlas articulates with the occipital, has a thin body, 



