SPINAL DURA MATER. 



375 



the coccyx ; and the cord and its membranes are to be divided opposite 

 the lower cervical vertebra?, and to be removed by cutting the bands that 

 attach the dura mater to the posterior ligament of the bodies of the ver- 

 tebrae. 



When the cord is taken out, place the anterior surface uppermost with 

 the lateral offsets widely separated. To show the arachnoid covering, the 

 dura mater is to be slit along the middle as far as the small terminal 

 fibrous cord before referred to; but the membrane is to be raised whilst it 

 is being cut through, so that the loose arachnoid on the cord may not be 

 injured. Lastly, fasten back the dura mater with pins. 



Fig. 122. 



LOWKR END OF THE DURA MATER, WITH ITS 

 CENTRAL AND LATERAL PROCESSES. (Mu- 

 seum University College, London.) 



a. Large sheath of the dura mater. 



6. Central fibrous band fixing it to the coc- 

 cyx. The lateral offsets encasing the 

 last two lumbar, and the five sacral 

 nerves, with the coccygeal nerve, are 

 also shown. Each nerve is marked by 

 the numeral, and the first letter of its 

 Dame. 



VIEW OF THE MEMBRANES OF THE'SPINAL 

 CORD. 



a. Dura mater cut open and reflected. 



6. Small part of the translucent arachnoid, left. 



h. Pia mater closely investing the spinal cord. 



c. Ligameutum donticulatum on the side of the 

 cord, shown by cutting through the ante- 

 rior roots of the nerves. 



d. Processes joining it to the dura mater. 



ff. Anterior spinal artery and the fibrous baud 

 (liuea splendens) on the cord. 



e. Anterior roots of the nerves, cut. 



/. Posterior, each entering a separate hole in 

 the dura mater. 



The arachnoid membrane (fig. 122, b) is the thin serous covering of the 

 cord which is immediately beneath the dura mater. Like the correspond- 

 ing membrane in the skull, it invests the spinal cord and lines the dura 

 mater, and consists thus of a visceral and a parietal part. 



