THE VERTEBRJE. 139 



oblique and decussating. The outer part of these intervertebral 

 ligaments is the most solid and hard; and they gradually 

 become softer till they are almost in the form of a glairy liquor 

 in the centre. The external fibrous part of each is capafcle of 

 being greatly extended, and of being compressed into a smaller 

 space, while the middle fluid part is incompressible, or nearly 

 so. The middle point is therefore a fulcrum or pivot, on which 

 the motion of a ball and socket may be made, with such a 

 gradual yielding of the substance of the ligament, in whatever 

 direction our spines are moved, as saves the body from violent 

 shocks, and their dangerous consequences. This ligamento- 

 cartilaginous substance is firmly fixed to the horizontal surfaces 

 of the bodies of the vertebrae, to Connect them ; in which it is 

 assisted by a strong membranous ligament, which lines all their 

 concave surface, and by a still stronger ligament that covers all 

 their anterior convex surface. 



The elastic substance seems to be in a state of compression 

 by the exterior ligament and the bones ; for, if a section be 

 made through a portion of the vertebrae and the intervertebral 

 substance, this substance will expand, so that its surface will 

 be much higher than that of the vertebrae, h is s_o elastic, and 

 so much confined, in some subjects, that a sharp knife, if plunged 

 into it will be gradually ejected when the hand is with- 

 drawn. 



The bodies of the vertebrae are, with some exceptions, 

 smaller and more solid above, but more spongy as they descend. 

 The cartilages between them are thick, and the surrounding 

 ligaments are strong in proportion to the size of the vertebrae. 

 By this disposition, the greatest weight is supported on the 

 broadest, best secured base, and the middle of the body is 

 allowed a large and secure motion. 



From each side of the body of each vertebrae, a bony bridge 

 or pedicle is produced backwards, and to one side ; from the 

 posterior end of which one slanting process rises, and another 

 descends. The smooth, and generally the flattest side of each 

 of these four processes is covered with a smooth cartilage ; and 

 the two lower processes of each upper vertebrae are fitted to 



