SPIXAL COLUMN. 



445 



tebral foramen, for the FlG - 123 ' 



passage of the spinal 



nerves. 



The spinous process, 

 formed by the junction 

 of the two lateral, is 

 situated on the posterior 

 median line, and consti- 

 tutes the most project- 

 ing part of the vertebra. 

 The series of these pro- 

 cesses,, one above the 

 other, presents a long 

 and prominent crest be- 

 hind, known as the spine. 

 The use of these processes is to give attachment to tendons 

 and muscles. The transverse project outward from the lat- 

 eral, nearly at right angles, and also give attachment to 

 muscles, and in the back sustain the ribs. 



The oblique or articular processes are two on each side 

 one superior, the other inferior. They arise, in common 

 with the transverse, from the lateral. Their surfaces are 

 smooth, covered with cartilage, and articulated with simi- 

 lar processes upon the adjacent vertebrae above and below. 



The body and processes thus arranged bound a foramen, 

 which, running through the whole series of vertebral bones, 

 constitutes the spinal canal, for lodging the spinal marrow. 



The structure of the body (Fig. 123) is extremely light 

 and spongy, consisting almost entirely of the cellular or 

 cancellated tissue of bone. The processes are much more 

 compact in their structure. The development of a vertebra 

 takes place generally by three points of ossification, one for 

 the body and one for each side. In addition to these prin- 

 cipal, there are five other accessory points, one for the 



FIG. 123 represents a Lumbar Vertebra its upper surface. 1 Spinous pro- 

 cess. 2 Same process connecting with the lateral lamina. 3 Superior artic- 

 ular process. 4 Transverse process. 5 Inferior articular process. 6 7 Body 

 of the vertebra. 9 Foramen for spinal marrow. 



