io8o 



HUMAN ANATOMY. 



a compact strand that, as the ascending portion of the nerve, courses beneath the 

 eminentia teres seen on the ventricular floor, close to the mid-line, until it bends 

 outward and, arching around the abducent nucleus, continues ventrally as the 

 emerging root-fibres. 



The ventral part of the inner area and the adjoining part of the middle one are 

 occupied by the field of the mesial fillet which, at the level under consideration, no 

 longer has its longest axis directed dorso-ventrally, but approximately horizontal. 

 The tract now appears as a modified oval, somewhat compressed from before back- 

 ward, the thicker inner end of which reaches the raphe while the tapering outer end 

 lies near the superior olive. The posterior longitudinal fasciciihis is seen as a com- 

 pact strand, immediately beneath the gray matter of the ventricular floor and at the 

 side of the raphe. To the outer side of the emerging facial fibres, and therefore in 



Fig. 935. 



MesencephaliL loot of V 

 Posterior longitudinal fasciculus 



Superior cerebellar peduncle 

 - Inltrior cerebellar peduncle 



Sensory trigeminal nucleus 



Middle cerebellar peduncle 



- -" ^^# H Motor trigeminal 

 nucleus 



Motor fibres of V 



;;^^^TrigeminaI nerve 

 Superior olive 

 Median fillet 



Deep transverse pontine fibres 



Pyramidal tracts 

 Middle transverse pontine fibres 



Transverse section of pons at ie\el J, big 919, showing root of trigeminal ner\e vvith its nuclei. X 3- 



Preparation by Professor Spiller. 



the lateral pontine area, appear the siibstantia gelatinosa and the associated spinal 

 root of the trigeminal nerve. Just behind the latter the desceiiding vestibular root 

 lies close to the inner side of the restiform body. The collection of nerve-cells 

 marking Deiters' nuclejis is seen beneath the ventricular floor in close relation with 

 the descending vestibular root. 



Sections passing at the level of Fig. 935, and, therefore, about three millimeters above 

 that of Fig. 933, show interesting details connected with the nuclei and roots of the trigeminal 

 nerve. At this l(='vel the nuclei and roots of the sixth and seventh nerves are no longer seen. 

 The median fillet appears on each side as a compressed oval, the long axis of which is hori- 

 zontal and whose inner end almost touches the raphe. Just above the outer end of the fillet, 

 the cerebral extremity of the superior olive is still visible, to which a few strands of transverse 

 fibres — the last of the trapezoid body — pass. The lateral boundary of the ventral part of the 

 pons is defined by a hugh tract of obliquely cut fibres that marks the entering sensory root of the 

 trigeminal nerve. On following this tract dorsally it is seen to enter a large mass of gray 

 matter, the sensory nucleus of the trigeminal nerve. This ganglion, composed of closely 

 packed small multipolar cells, corresponds to an accumulation of the substantia gelatinosa, 

 which, it will be remembered, is to be seen in all the preceding lower levels intimately related 



