456 LIGAMENTS OF THE SPINE. 



Their thickness varies in different parts. In the neck 

 and loins the thickness is greater before than behind 

 while in the back it is less. The curves of the spine are 

 due, in great measure, to this substance. A transverse 

 Section of this ligament shows its fibres to run in a concen- 

 tric form, being very close and compact near the surface, 

 and as they approach the centre, spaces or interstices are 

 left, containing a soft, pulpy, semi-fluid substance, while 

 in the centre, the spaces become still wider and more cellu- 

 lar, and present still more of the pulpy matter. This cen- 

 tral pulpy and conical body is a movable, elastic fulcrum, 

 upon which the different vertebrae turn. It is more abun- 

 dant, softer, whiter, and more transparent, in proportion, in 

 infancy, than in any after period. In old age it diminishes 

 both in quantity and elasticity, which accounts, in some 

 measure, for the stiffness of the spine in old people. 



The use of the intervertebral ligaments is manifold. 

 They, in common with those just described, tie the several 

 vertebrae together ; they help to form the spinal canal, 

 give sockets to the heads of the ribs, allow the flexibility 

 of which the spine is capable ; and, by their elasticity, pre- 

 serve the spine of its uniform height : they also lessen the 

 effects of shocks from concussion. 



4. Ligamenta subflava, or yellow ligaments, (Fig. 134.) 

 These ligaments close the spinal canal behind, and are 

 FIG. 134. situated between the posterior 



arches of the different vertebra?. 

 They are found between all the 

 vertebrae from the axis to the sa- 

 crum. They are in pairs, on each 

 side of the median line, and are 

 twenty-three in number. They ex- 

 tend from the inferior margin of 

 the lamina above, to the superior 

 margin of the corresponding one 

 below. Their structure consists of yellow elastic tissue. 



Fig. 134 represents the Yellow Ligaments (ligamenta flava.) a a One pair 

 of the yellow ligaments. 6 Capsular ligament of the one^ side. 



