CHAPTER IV. 



Spinal column. Thorax. Upper limb ; shoulder ; arm, fore-arm, 

 hand. Lower limb; hip, thigh , leg, foot. 



Spinal column. The spinal column is the foundation to 

 which all the other parts of the skeleton are adapted. It is 

 composed of seven cervical vertebrae, twelve dorsal and five 

 lumbar vertebrae, and is terminated by the sacrum and 

 coccyx. Throughout its whole length runs the vertebral 

 canal, which holds the spinal marrow, and communicates 

 with the cavity of the skull. Each vertebra is composed of 

 a body, two articular processes, two transverse processes, and 

 a spinous process. The body, the anterior portion of the 

 vertebra, is cylindrical, and forms a layer of the column. 

 The articular processes, placed at the sides, serve to unite the 

 vertebrae together; and \hetransverseprocesses give attachment 

 to the ligaments, muscles, and in the dorsal regions to the 

 ribs. The spinous process, the posterior portion of the verte- 

 bra, forms that series of projections which has given to the 

 vertebral column the name of the spine. The spinous process 

 bifurcates into two plates which complete the ring or verte- 

 bral orifice formed by each vertebra, and the open space in 

 which forms a segment of the vertebral canal. Numerous 

 and powerful ligaments combine to unite the vertebrae. Be- 

 tween their bodies fibrous disks in the form of lentils are 

 placed, which adhere intimately to the articular surfaces ; 

 they are formed of concentric layers, and near the centre 

 there is a spongy substance saturated with a fluid analogous 

 to the synovia. These disks or intervertebral ligaments, 

 besides binding together the bodies of the vertebrae, serve 



