THE NERVOUS SYSTEM 



157 



however, run down the direct and crossed pyramidal tracts 

 of the same side. 



2. The fibres of the descending antero -lateral tract take 

 origin in a mass of nerve cells, which lies in the dorsal and 

 lateral part of the pons Varolii (Deiters' nucleus) (Fig. 86, 

 Deit.). 



C. Commissural Fibres. 



(1) The antero-lateral basis bundles of the cord form in 

 the medulla a strong band of fibres connecting the grey 



V7/7 AccN 



FIG. 84. Cross Section of Medulla through the Olive. The Central Canal has 

 opened out to form the Floor of the Fourth Ventrical, 4th V. ; the Lateral 

 Columns are passing out to form the Inferior Peduncles of the Cerebellum ; 

 F. , Fillet; O. , Inferior Olivary Nucleus; />., Anterior Pyramids; Rest., 

 Fibres of Kestiform Body; F., Ascending Root of Fifth Nerve; VIII. 

 Ace. N., Accessory Nucleus of the Eighth Nerve. (After BRUCE.) 



matter at different levels, and known as the posterior longi- 

 tudinal fasciculus. 



(2) A set of fibres run from each olivary body across the 

 middle line to the dentate nucleus of the cerebellum of the 

 opposite side. 



3. Cranial Nerves. 



(The physiology of these should be studied while dissecting 

 them.) The nerves springing from and entering the medulla, 

 do not come off in the same regular fashion as the spinal 

 nerves. The outgoing fibres of each spring from a more or 



