LIGAMENTS OF THE SPINE. 



133 



centage very accurately, and there is much variation. The following proportions 

 are, therefore, only approximate. The disks form in the cervical region forty per 

 cent., in the thoracic, twenty per cent., and in the lumbar, thirty-three per cent, of 

 the length of the spine. 



Fig. 162. 



Odontoid process of axis Transverse ligament 



Anterior 

 arch of 

 atlas 



Posterior at- 

 lanto-axial 

 ligament 



Body of first 

 thoracic 

 vertebra 



Interspinous 

 ligament 



Seventh cervi- 

 cal spine 



Intervertebral 

 foramen 



Lamina 



Anterior and Posterior 

 Common Ligaments. — The 



bodies are connected by short 

 fibres surrounding the disks, 

 and by long bands which are 

 only partially separable from 

 the general envelope. The a?^- 

 tcrior common ligament^ (Figs. 

 163, 165) begins at the axis 

 and extends to the sacrum. It 

 consists of shorter and longer 

 fibres blending with the peri- 

 osteum and springing from the 

 edges of the vertebrse and from 

 the disks, to end at similar 

 points on the next vertebra, or 

 on the second, third, fourth, or 

 fifth. The borders are not 

 sharply defined. T\\^ posterior 

 common liganicnt'^ ( Fig. 164) 

 is a much more distinct struc- 

 ture. It arises from the back 

 of the body of the axis, re- 

 ceiving fibres from the occipito- 

 axial ligament, and runs to the 

 sacrum. It also is attached 

 to the disks and the edges of 

 the bodies, but possesses a dis- 

 tinct margin, which, except in 

 the neck, expands laterally 

 into a series of points at the 

 intervertebral disks. It stands 

 well out from the middle of 

 the bodies, bridging over the 

 veins of the larger ones. 



LIGAMENTS CONNECT- 

 ING THE LAMINA AND 

 THE PROCESSES. 



Thearticularprocesses * 



(Fig. 165) are coated with 

 hyaline articular cartilage and 

 surrounded by loose capsules, 

 with which, especially in the 

 thorax, the ligamenta subflava 

 are inseparably connected, pre- 

 venting by their tension the 

 occurrence of folds. 



The ligamenta subflava* ( Figf- 163) are elastic membranes of considerable 

 strength connecting the laminae from the axis to the sacrum. They are particularly 

 developed in the lumbar region. As just mentioned, they encroach on the side of 

 the capsules towards the canal. They also extend a short distance under the spinous 

 processes. 



The supraspinous ligament (Figs. 162, 163) extends as a well-marked cord 



' Lig. longitudinale anterius. ^ Lig. longitudinale posterius. ^ Ligg. flava. 



Interverte- 

 bral disk 



Tenth tho- 

 racic ver- 

 tebra 



Ligamentum 

 subfiavum 



Supraspinous 

 ligament 



Median section of upper half of spine. 



