DISSECTION OF THE HEAD AND NECK 201 



Turn the head of the cadaver forcibly to the left; raise the 

 posterior part of the right cerebral hemisphere and expose the 

 broad tentorium cerebelli. Cut through the tentorium along its 

 attachment to the superior angle of the temporal bone (anynln* 

 superior pyramidis) and, with the point of the knife, shove the 

 tentorium backward out of the way. Now turn the head forcibly 

 to the right and divide the tentorium on the left side in a similar 

 manner. 



Next divide successively, from before backward 



(a) Trigeminal nerve (N. trigeminus) . 



(aa) Larger (sensory) root (portio major). 



(ab) Smaller (motor) root (portio minor}. 



(b) Abducent nerve (N. abducens). 



(c) Facial nerve (N. facialis). 



(d) Intermediate nerve (N. intermedius) (0. T. pars intermedia of Wris- 



berg). 



(e) Acoustic nerve (N. acusticus) (0. T. auditory nerve). 



(ea) Vestibular root (radix vestibularis) . 



(eb) Cochlear root (radix cochlearis}. 



(f) Glossopharyngeal nerve (N. glossopharyngeus ) . 



(g) Vagus nerve (N. vagus). 



(h) Accessory nerve (N. accessorius) (0. T. spinal accessory). 

 (i) Hypoglossal nerve (N. Tiypoglossus). 



Now thrust a long, narrow, straight-bladed knife into the ver- 

 tebral canal, cut the A. vertebral is on each side and the roots of 

 the first cervical nerve on each side; just below this level sever 

 the spinal cord, as nearly transversely as possible, with the 

 knife or, better, with Pick's myelotome. 



The brain may now be easily removed from the skull, usually 

 by gravity. Tie a thread around the basilar artery (A. basi- 

 laris) and suspend the brain in a jar of ten per cent, formalin 

 solution; in a few days it will be hardened sufficiently for study. 

 The brain may be kept for a long time in formalin without 

 injuring it for gross anatomical study. 



Dura Mater Encephali. 



The study of this membrane should now be resumed. Exam- 

 ine its relations to the cerebral nerves and to the bones of the 

 base of the skull. At the partitions formed by processes of the 

 dura mater the falx cerebri has already been studied. The stu- 

 dent should now examine thoroughly 



(a) Tentorium cerebelli. 



Note its form, position, and nttnclmuMits. In it run the important 



