I074 



HUMAN ANATOMY. 



as a large irregularly crescentic tract of transversely cut fibres that occupies the 

 greater part of the periphery. (2) The descetidmg root of the vestibular 7terve is seen 

 to the inner side of the dorso-mesial border of the restiform body as a field of loosely 

 grouped bundles of cross-sectioned nerve-fibres. (3J The fasciculus solitarius, or 



Fig. 928. 



Ventricular roof 



Fasciculus solilanus 



Dorsal nucleus of X 



Nucleus of XII 

 I Post. long. 



Restiform 

 body 



Root-fibres v ■^ fj 

 of X nerve ^ 



Nucleus ambijuus 

 Root-fibres of 



Restiform body 



Descending 

 vestibular root 



Gray column 

 of vestibular root 

 Form.retic.grisea 

 Form, retic. alba 



ary stratum 

 lan fillet) 



vary nucleus 



Pyramidal tiacts 



Transverse section of medulla at level F, Fig. 919; ventricular floor is wide; restiform body well established ; 

 descending root of vestibular nerve is seen. X 5. Preparation by Professor Spiller. 



Fig. 



929. 



descending root of the vagus and glosso-pharyngeal nerves, shows as a conspicuous 

 transversely cut bundle which lies ventro-mesially to the vestibular root. (4) The 

 descending root of the trigeminal nerve is easily identified as a superficial crescentic 

 field that on its mesial aspect encloses the remains of the substantia gelatinosa Rolandi. 

 The lateral area, between the diverging vagus and hypoglossal root-fibres, is 

 chiefly occupied, in addition to (i) the i?iferior olivary and (2) dorsal accessory 

 olivary nucle7is, by the feltwork of fibres producing the reticular formation. In con- 

 trast to that within the 

 anterior area, the retic- 

 ulum within the lateral 

 area contains a con- 

 siderable amount of 

 diffuse gray matter be- 

 tween its fibres, and, 

 hence, is known as (3) 

 \hit form alio rcticulai'is 

 grisca. Accessions to 

 the irregularly distrib- 

 uted nerve-cells occur 

 as two more definite col- 

 lections ; one of these, 

 (4) the 7iucleus am- 

 big7ius. consists of an 

 inconspicuous group of 

 large cells lying about 

 the middle of the gray 

 reticular substance and is of importance as the nucleus of origin of at least part of 

 the motor fibres of the vagus nerve. The other (5), the nucletis lateralis, includes 

 an uncertain aggregation of medium sized cells, situated near the periphery and ventral 



Nerve-cell 



Transverse 

 fibres 



Longitudinal 

 fibres 







Portion of formatio reticularis grisea, showing nerve-cells and interlacing 

 transverse and longitudinal fibres. X 130- 



