884 



THE NERVOUS SYSTEM 



penetrate the dura. Along its dorsal aspect the spinal dura mater is practically free 

 from the wall of the vertebral canal. (5) At its lower and funnel-shaped extremity, 

 opposite the second sacral vertebra, the tube suddenly contracts into a filament 

 extending into the coccyx and breaking up into a number of processes which become 

 continuous with the periosteum of the dorsal surface of the coccyx. This filament 

 is the coccygeal ligament or filum of the dura mater, and its attachment may be 

 considered t lie lower fixation-point of the spinal dura mater. The extent of the tube is 

 maintained chiefly by means of the two fixation-points, for all the other attachments 

 are sufficiently loose to permit of the movements of the vertebral column. 



FIG 656 DORSAL ASPECT OF THE MEDULLA OBLONGATA AND SPINAL CORD WITH THE DURA 

 MATER PARTIALLY REMOVED. (Hirschfeld and Leveilte.) 



MIDDLE 

 PEDUNCLE 



INFERIOR ! 



PEDUNCLE 



CLAVA 



_ SUPERIOR PEDUNCLE 

 OF Till-: CBREBELLW 



_ MEDIAL i.ii.\i:rri'i>i- 



XAL .ST/.'T.v 

 GLtllffUl-l'llA I! \X<: i:l ".V 



VAQUa 



SPINAL ACCESSORY 



Ligaraentum 

 denticulatum 



POSTERIOR LONGI- 

 TUDINAL SULCUS 



A VENTRAL ROOT 

 A DORSAL ROOT 



VI. 



VII. 



VIII. 



.S7V.Y.I /, 

 <,A.\i:LION 



The inner surface of the spinal dura mater appears smooth, but upon closer ex- 

 amination it is found to be connected with the arachnoid by a few delicate subdural 

 trabecula 1 occasional fine strands of connective tissue bridging the subdural space 

 (fig. 665). Along its lateral aspects the inner surface is at intervals quite firmly at- 

 tached to the pia mater by the dentations of the ligamenta denticulata, which are 

 prolonged through the arachnoid. Further, it is continuous at intervals with both 

 the pia mater and arachnoid by way of the connective-tissue sheaths of the nerve-roots 

 which are prolonged from the pia and blend with the dura mater in the passage of the 



