428 



PHYSIOLOGY 



CHAP. 



ascending from the cord must be distinguished from those which 

 take origin in the medulla oblongata. 



The "afferent spinal fibres run in the lateral columns of the. 

 cord ; these are the direct cerebellar tracts of Flechsig, which 

 ascend through the restiform body to the vermis of the cerebellum. 

 The fibres of these bundles spring for the most part from the cells 

 of Clarke's column on the same side, and as the collaterals of the 

 posterior roots run to these cells there is thus au indirect connec- 

 tion between the dorsal roots and the cerebellum. But, according 

 to Edinger, Obersteiner, and Thomas, there is also a direct connec- 

 tion between the posterior roots and the cerebellum, as certain 

 fibres of the posterior column turn dorsalwards and lateralwards as 

 external posterior arcuate fibres, and join the restiform body, to 

 run with the fibres of Flechsig's bundle to the vermis. 



From certain observa- 

 tions of Ferrier and 

 Turner it seems probable 

 that the nuclei of the 

 posterior columns also 

 send fibres to the cere- 

 bellum via the restiform 

 body, but this has not yet 

 been proved. 



A larger proportion of 

 the fibres of the inferior 

 cerebellar peduncle come 

 from the bulb than from 

 the cord. Atrophy of 

 the inferior olive, associ- 

 ated with atrophy of the opposite side of the cerebellum, as first 

 described by Meynert and confirmed by subsequent observers- 

 shows that there is a crossed relation between the inferior olive 

 and the cerebellum, by way of fibres that ascend through the 

 restiform body. Other fibres spring from the cerebellar cortex 

 and descend to the olive of the opposite side ; in fact, after uni- 

 lateral cerebellar extirpation there is a considerable atrophy of the 

 inferior olive of the opposite side (Fig. 228, a, &). 



According to Edinger, a bundle of afferent fibres, which he 

 terms the direct sensory cerebellar tract, takes origin in the main 

 nucleus of the acusticus, the nucleus of Deiters, and the nucleus of 

 Bechterew, and ascends through the internal segment of the 

 inferior cerebellar peduncle to the cerebellum, where it ends in 

 the nucleus fastigii and the nucleus globosus (Fig. 229). This 

 bundle is joined by fibres from the trigemiiius, vagus and accessory 

 nuclei. As the fibres of the vestibular nerve terminate in the 

 vestibular nucleus there is thus an indiiect relation between the 

 semicircular canals and these internal nuclei of the cerebellum. 



Fio. 227. Plan of afferent and efferent paths that run 

 through the middle cerebellar peduncle to establish 

 reciprocal relations between the cerebellum and the. 

 cerebrum. (Mingaxzini.) 



