184 



HEAD AND NECK 



downwards through the sacral canal from the extremity of the 

 medulla spinalis (O.T. spinal cord). 



The cylindrical tube of spinal dura mater does not lie 

 free within the vertebral canal, although its attachments are 

 of such a nature that they do not in any way interfere with 

 the free movement of the vertebral column. Above, the dura 

 mater is firmly attached to the second and third cervical 



.Dura mater 

 Arachnoid 

 Ligamentum denticulatum 



Arachnoid 



Posterior nerve-root 

 Spinal ganglion 



Anterior branch 

 of nerve 



Posterior branch 

 of nerve 



Dura mater 



Anterior nerve-root 

 (cut) 



Posterior nerve-root 



Anterior nerve-root 

 (cut) 



Ligamentum 

 denticulatum 



Pia mater 



Anterior nerve-root 



FIG. 74. Membranes of the Medulla Spinalis (O.T. Spinal Cord), and the 

 mode of origin of the Spinal Nerves. 



vertebrae, and around the margin of the foramen magnum ; 

 below, the filum terminale, on which it terminates, can be 

 traced as far as the dorsal aspect of the coccyx, where it is 

 lost by blending with the periosteum. On either side the 

 spinal nerve-roots, as they pierce the dura mater, carry with 

 them into the intervertebral foramina tubular sheaths of the 

 membrane, which are attached to the margins of the foramina, 

 whilst, anteriorly, loose fibrous prolongations more numerous 

 above and below than in the dorsal region connect the tube 

 of dura mater to the posterior longitudinal ligament of the 



