396 THE MECHANICAL FUNCTIONS. 



(i) are affixed to the ends of each spinous 

 process. In many cases, instead of being thus 

 placed in aline with these processes, they appear 

 at a little distance, as if they had slipped from 

 their proper situations ; they are then found 

 between the spinous processes, and receive the 

 name of interspinous bones. 



The spinous processes have a tendency, when 

 their developement proceeds, to divide into two 

 branches, and this bifurcation frequently takes 

 place also in the interspinous bones. The trans- 

 verse processes likewise occasionally develope 

 accessory pieces, as is found to be the case in 

 some reptiles ; but in other instances they undergo 

 a gradual change of position, as we follow them 

 backwards along the spinal column, where they 

 descend towards the abdominal region. 



The flexibility of particular portions of the 

 spinal column is regulated by the size and form 

 of its processes. When these are much deve- 

 loped, they necessarily obstruct the flexion of 

 the vertebrae in the directions in which they are 

 situated : when they are small, no such hind- 

 rance arises, and the spine is free to move in all 

 directions. Thus, when we see the spinous pro- 

 cesses much enlarged, while the transverse pro- 

 cesses are small, we may infer that the spine is 

 incapable of any bending in that direction ; but 

 that it has the power of free lateral flexion. This 



