454 



PHYSIOLOGY 



between the development of each cerebellar hemisphere and the 

 contralateral cere'bral hemisphere. Atrophy of one half of the 

 cerebrum brings about atrophy of the opposite hemisphere of 

 the cerebellum. 



THE SUPERIOR PEDUNCLE. By this path fibres from the superior 

 corpora quadrigemina, i.e. from the terminations of the optic nerve, 

 pass into the cortical grey matter of the cerebellum (Fig. 201). 



EFFERENT TRACTS. The 

 cerebellar cortex must be regarded 

 as a receiving rather than as a 

 discharging station. Stimulation 

 of it has little effect unless strong- 

 currents are employed, and a motor 

 response is obtained more easily 

 the deeper the electrodes are sunk 

 below the grey matter. The fibres 

 which form the axons of the cells 

 of Purkinje pass partly towards 

 the pons by the middle peduncle, 

 largely, however, towards the roof 

 nuclei, where they terminate. These 

 nuclei form the efferent stations 

 of the cerebellum. From them 

 fibres pass in various directions. 

 A large bundle leaves the dentate 

 nucleus, runs into the superior 

 peduncle, or brachium, and passing 

 deeply across to the tegmentum of 

 the opposite side, traverses the red 

 nucleus to end in the subthalamic 



& <* *e opposite side of the 



v, GEHUCHTEN.) brain. A certain number of fibres, 



OT, optic thalamus ; BN, red nucleus ; chiefly derived from the central 



PCT, posterior cerebellar tract ; ACT, . . . .. 



anterior cerebellar tract ; v, fifth nerve, nuclei, SUCh as the nucleus tastlgll, 



pass forward to the corpora quadri- 

 gemina chiefly on the same side. From the cerebellum itself no 

 direct tract runs into the spinal cord. The nuclei of Deiters 

 and of Bechterew, which are connected with the endings of the 

 vestibular nerve, are, however, closely associated with the roof 

 nuclei, and give rise to descending fibres which pass into the 

 antero- lateral region of the cord as the vestibulo- spinal tract. 



The cerebellum is therefore a receiving station not only for impulses 

 which arise in the skin and eyes, i.e. on the surface of the body, 

 but especially for those which have been defined as proprioceptive, 



