THE CEREBELLUM. 893 



mechanisms in the tegmental region of the pons that can, on excitation, 

 evoke convulsive movements of the trunk, neck, and limbs, and can be 

 easily brought into action reflexly by stimulation of the trigeminal 

 nerve. 



As a conductor the floor of the raetencephalon contains the mesial fillet, 

 with its constituents from the dorsal column nuclei, etc., as elsewhere 

 described. Near it the lateral fillet contains ascending paths from the end 

 nuclei of the auditory nerves, chiefly contralateral. The superior olive is 

 probably of auditory function, to judge from its close connection with this 

 path. In the more lateral region, ascend paths from the ventrolateral column 

 of the spinal cord, chiefly from mediate cells in the opposite half of the grey 

 matter. Some of this path is probably connected with " pain." They are on 

 their way to the roof of the metencephalon (cerebellum) and the mesen- 

 cephalon. Transection of the dorsal portion of the metencephalic floor to one 

 side only of the median sagittal plane produces (monkey) complete anaesthesia 

 (including analgesia) of the contralateral half of the body, without any 

 paralysis. 1 Of the paths connected with the cerebellum a most notable is, 

 the ascending of the inferior peduncle coming from the lateral column of the 

 cord and Clarke's column of cells (uncrossed mediate cells of the cord). There 

 is also a patli conducting upwards from this region into the crossed corpus 

 striatum. 2 There descend into the pons three main paths from the cerebral 

 cortex, one from the frontal cortex which ends in the grey matter of the pons, 

 a second from the temporal cortex which ends in the grey matter of the pons, 

 and a third, the pyramidal, which only in small part terminates in the pons, in 

 its motor nuclei. Of these the fronto-pontine is the most lateral, the temporo- 

 pontine the most median. Among the fibres of the pyramidal tract which, end 

 in the pons, some have been traced to the crossed nuclei of the motor fifth 

 and seventh, and some also to the homonymous nuclei. From the " reticular 

 formation " of the pons a descending path passes into the ventrolateral columns 

 of the cord, partly decussating in its descent ; the crossed path lies more dorsal 

 in the cord than the uncrossed. Of their function nothing can with certainty 

 be said. There pass through the reticular formation of the pons paths 

 descending from the mesencephalon (red nucleus and anterior corpus quadri- 

 geminum) to the ventro-lateral column of the spinal cord. Both these paths are 

 mainly crossed ones. The posterior longitudinal bundles form two more paths, 

 chiefly descending. They in part mediate between the motor cell groups of 

 the ocular and other muscles. This explains, perhaps, the elicitation of eye- 

 movements, like those obtainable from the anterior corpus quadrigeminum, from 

 the floor of the fourth ventricle behind the nucleus abducens. 3 



The Cerebellum. 



Excitation.— Ferrier 4 discovered (1873) that faradic excitation of 

 the cortex of certain parts of the superior vermis, and postero-superior part 

 of the lateral lobe, evokes in the dog and cat conjugate movement of the 

 eyes toward the homonymous side ; in the rabbit the movement obtained 

 from the lateral lobe was sometimes not conjugate. Similar conjugate 

 movements he obtained later 5 in the monkey, also in that animal pure 

 conjugate upward and downward movements of the eyes elicitable from 

 the middle line of the superior vermis. From the flocculus was elicited 



1 Ferrier and Turner, Phil. Trans., London, 1898. 



2 Wallenberg, Neurol. Centralbl., Leipzig, 1898, Bd. xvii. S. 293. 



3 Knoll, Sitzungsb. d. k. Akad. d. Wissensch., Wien, July 1886, S. 239. 



4 West Riding Lun. Asyl. Hep., London, 1873, vol. iii. 



5 "Functions of the Brain," London, 1876. 



