THE MEDULLA OBLONGATA. 



1075 



from the trigeminal root. A separate group of somewhat larger cells, nearer the 

 ventral border of the trifacial root, has been designated the nucleus lateralis dorsalis, 

 and by KoUiker regarded as belonging to the origin of the spinal accessory nerve. 



Cochlear fibres crossing Descending root of 



restiform body vestibular nerve 



Fig. 930. 



Median 

 Nucleus vestibular 

 of IX nicleus 



Restiform 



Root of IX nerve 



Post. long. 



fasciculus 



Restiform 



bodv 



Substantia gelatmosa Av" 



Formatio retiCLlans alba 



Inferior olivary bodj 



Fibres of IX nerve 

 Spinal root of V neive 

 Substant i gelatinosa 

 Formatio reticularis grisea 



Pjramidal tracts 



Transverse section of medulla at level G, Fig. 919; ventral part is narrower, whilst dorsal part is expanded owing 

 to increased size of restiioim oodies. X 4- Preparation by Professor Spiller. 



In a general way the cells of these nuclei (ambiguus and lateralis) of the substantia 

 grisea may be regarded as the analogues of the lateral horn-cells of the cord, just as 

 those of the hypoglossal nucleus resemble the anterior root-cells of the spinal nerves. 

 The anterior area, between the mid-line and the hypoglossal root-fibres, is 

 occupied ventrally by ( i ) the pyramidal tract, which appropriates the entire width 

 of the field with the exception of a very narrow peripheral zone that intervenes 



Fig. 931. 



Nerve- Longitudinal Transverse 

 cell fibres fibres 



Median raphe 



Portion of transverse sectioihof medulla showing median raphe and adjacent formatio reticularis alba. X 130- 



between the pyramidal fibres and the surface along the median fissure and the ventral 

 aspect of the medulla. This zone is traversed by (2) the anterior superficial arcuate 

 fibres, among which is lodged an irregular column of nerve-cells that constitute (3) 



