250 Mammalia. 



Dissection of the Eighth and Ninth Pair of Cerebral 

 Nerves, and of the Sympathetic System at the base of 

 THE Skull. The Student will first cut througli the par- 

 occipital process near to the Skull, and turn it forwards, and 

 fix it in that position with a set of hooks and chains : by this 

 means he will be enabled to get at, and dissect out, the bundle 

 of nerves that lie but little below the fat in the cavity between 

 the par-occipital process and the external aspect of the occi- 

 pital condyle. 



This bundle of nerves consists of, in order from back to 

 front, the following principal factors : the Ninth or Hypo- 

 glossal Nerve leaves the skull through the anterior condyloid 

 foramen, and is crossed at about ^in. from the foramen by 

 the Spinal branch of the Spinal Accessory ; this spinal branch 

 joins the course of a stout nerve called the Pneumogastric or 

 Vagus just before it crosses the Hypo- glossal, and these may 

 be traced back together to the * foramen lacerum basis cranii,' 

 by which they take exit from the skull. Next adjoining this 

 stout nerve-branch is the fine Glossopharyngeal Nerve , which 

 leaves the skull at the same spot with the Yagus ; an& then 

 lies along the external surface of a nodulation of a pinkish 

 hue ; this nodulation is the First Cervical Ganglion of the 

 Sympathetic System. 



But in order to get at the roots of these nerves it will be 

 necessary to take the saw and first cut through the occipital 

 condyle down to the condyloid foramen, and break it ofi" 

 with the chisel, thus exposing the root of the Hypo-glossal 

 nerve ; and, secondly, to saw down from the posterior side of 

 the Facial nerve to the cranial exit of the conjoined Eighth 

 pair of nerves, separate the grooves with the chisel, and then 

 cut through the remaining pedicle of bone with the bone nip- 

 pers, by which means the ganglia at the root of the Eighth 

 pair of cranial nerves will be disclosed. It will now be well 

 to trace each of these nerves forwards. 



