774 



NEUROLOGY 





end and the pons there is a slight depression to which the roots of the facial nerve 

 are attached. The external arcuate fibers wind across the lower part of the pyra- 

 mid and olive and enter the inferior peduncle. 



The posterior district (Fig. 686) lies behind the postero-lateral sulcus and the 

 roots of the accessory, vagus, and the glossopharyngeal nerves, and, like the lateral 

 district, is divisible into a lower and an upper portion. 



Trochlear nerve 



Trigeminal nerve 



Facial nerve 

 Acoustic nerve 



Superior peduncle 

 Middle peduncle 

 'nferior peduncle 



Blossopharyngeal 

 nerve 



Vagus nerve 

 Accessory nerve 

 (cerebral part) 

 Hypoglossal nerve 



Accessory nerve 

 (spinal part) 



Post, roots of first 

 cervical nerve 



Medulla spinalis 



Dura mater 

 (laid open) 



Vertebral artery 

 Clava 



Fasciculus ntneatus 



Fasciculus yracilis 



FIG. 686. Upper part of medulla spinalis and hind- and mid-brains; posterior aspect, exposed in situ. 



The lower part is limited behind by the posterior median fissure, and consists 

 of the fasciculus gracilis and the fasciculus cuneatus. The fasciculus gracilis is 

 placed parallel to and along the side of the posterior median fissure, and separated 

 from the fasciculus cuneatus by the postero-intermediate sulcus and septum. 

 The gracile and cuneate fasciculi are at first vertical in direction ; but at the low r er 

 part of the rhomboid fossa they diverge from the middle line in a V-shaped manner, 

 and each presents an elongated swelling. That on the fasciculus gracilis is named 

 the clava, and is produced by a subjacent nucleus of gray matter, the nucleus 

 gracilis; that on the fasciculus cuneatus is termed the cuneate tubercle, and is like- 

 wise caused by a gray nucleus, named the nucleus cuneatus. The fibers of these 

 fasciculi terminate by arborizing around the cells in their respective nuclei. A 

 third elevation, produced by the substantia gelatinosa of Rolando, is present in 

 the lower part of the posterior district of the medulla oblongata. It lies on the 



