242 LABORATORY MANUAL OF HUMAN ANATOMY 



nerves (Nn. sacrales, L-V.), and the coccygeal nerve (N. coccy- 

 geus}. Note the subdivision of each spinal nerve trunk into an 

 anterior and a posterior ramus. Observe the roots of the spinal 

 nerves (radices nervorum spinalium). Where does the ventral 

 root (radix anterior) fuse with the dorsal root (radix poste- 

 rior) 1 Note the ganglion (ganglion spinale) on the latter. 

 What are the fila radicularia? Observe the relative lengths of 

 the various nerve roots. How do you account for this? Which 

 are the largest and which the smallest nerve roots? Examine 

 the cauda equina carefully. How do the nerves leave and enter 

 the vertebral canal ? Look for the ramus meningeus. 



Removal of Spinal Cord. 



Divide each spinal nerve trunk midway between the point of 

 fusion of its two roots and the point of division into an anterior 

 and a posterior ramus. 



Cut through the cord at the level of the first cervical nerve. 

 Lift the cord and its membranes gently from the vertebral canal 

 and transfer to formalin for subsequent study. 



THE SPINAL COED. 

 Blood-vessels of the Spinal Cord. 



As a rule, special injections are necessary to demonstrate the 

 blood-vessels of the cord well, but a good deal can be made out 

 in ordinary cadavers. Study the following : 



Arteries. 



(a) Branches of vertebral artery (A. vertebralis). 



(aa) Spinal rami (rami spinales). 



(ab) Posterior spinal artery (A. spinalis posterior). 



(ac) Anterior spinal artery (A. spinalis anterior). 



(b) Branches of ascending cervical artery (A. cervicalis ascendens). 



(ba) Spinal rami (rami spinales). 



(c) Branches of highest intercostal artery (A. intercostalis suprema). 



(ca) Spinal rami (rami spinales). 



(d) Branches of intercostal arteries (Aa. intercostales) . 



(da) Spinal ramus of posterior ramus (ramus spinalis rami pos- 

 terioris). 



(e) Branches of lumbar arteries (Aa. lumbales). 



(ea) Spinal ramus (ramus spinalis). 



(f) Branch of iliolumbar artery (A. iliolumbalis) . 



(fa) Spinal ramus (ramus spinalis). 



(g) Branches of lateral sacral artery (A. sacralis lateralis). 



(ga) Spinal rami (rami spinales). 



