218 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



medullary substance of the vermiform lobe (nucleus fastigii, n. glo- 

 bosi, and the n. embolif ormis) . The axons of many of the Purkinje 

 cells of the cortex terminate in these subcortical nuclei, and the 

 efferent path from the cerebellum is then continued by new neurons. 

 Thus, the fibers of the superior peduncles of the cerebellum arise 

 chiefly from the dentate nuclei, and only indirectly from the cor- 

 tex. The anatomical connections, afferent and efferent, between 

 the cerebellum and other parts of the nervous system are very com- 

 plex and not yet entirely known. Without attempting to recall 

 all of these connections, which will be found described in works upon 

 anatomy or neurology, emphasis may be laid upon those which are 

 at present helpful in discussing the physiology of the organ. 



1. Connection with the Afferent Paths of the Cord. The ascending 

 fibers in the posterior columns are connected, through the nuclei of 

 Goll and Burdach, with the cerebellum, the fibers passing by way 

 of the inferior peduncles (restiform bodies). So also the fibers of 

 the tracts of Flechsig and Gowers terminate eventually in the cere- 

 bellum, as explained on p. 164. Whatever else may be their func- 

 tions, the fibers of these tracts undoubtedly convey impulses of 

 the muscle sense, and we have, therefore, the important fact that 

 these fibers (as a system) terminate in part in the cerebellum and 

 in part, by way of the median fillet, in the cerebrum. 



2. Connections with the Vestibular Branch of the Eighth Cranial 

 Nerve. This branch, arising in the semicircular canals and utriculus 

 and sacculus, ends in the pons in several nuclei (lateral or Deiters's, 

 median and superior) and these in turn are connected by fibers, 

 running probably in both directions, with the cortex of the cere- 

 bellum and with its subcortical nuclei. This connection is most 

 important physiologically, as it would seem to make the cerebellum 

 a center for impulses arising in these parts of the internal ear. As 

 we shall see, ablation of the cerebellum and destruction of the semi- 

 circular canals give very similar results upon animals. 



3. Connections with the Cortex of the Cerebrum. A large system of 

 fibers cerebro-ponto-cerebellar system (see Fig. 77, A) makes a 

 connection between the cortex cerebri and cortex cerebelli. They 

 emerge from the cerebellum by way of the middle peduncles, cross 

 the mid-line, and end in gray matter (pontal nuclei) in the pons; 

 thence their course is continued by new neurons, which pass for- 

 ward in the crus cerebri and internal capsule to make connections 

 with the cortex of the frontal lobe. The connection is, therefore, 

 a crossed one, the right cerebrum being associated with the left 

 cerebellar hemisphere. This system of fibers furnishes a mechan- 

 ism by which the cerebellar activity may be associated with and 

 influence the activity of the motor areas of the cerebrum. 



4. Connections with the Midbrain and Cord. The fibers of the 



