886 



THE CENTRAL NERVOUS SYSTEM 



The middle peduncle is in the main a link between the cerebellar 

 cortex and the cerebral cortex of the opposite side, through the relay 

 of the pontine grey matter. Most of the fibres in it are afferent in rela- 

 tion to the cerebellum, their cells of origin being situated in the nuclei 

 of the pons, and sending their axons across the middle line to end in the 

 cerebellar cortex. 



The superior peduncle connects chiefly the dentate nucleus of one 

 side with the cortex of the opposite cerebral hemisphere through the 

 red nucleus of the tegmentum of the crus cerebri and the optic thalamus 

 on the opposite side. The great majority, or perhaps all, of its fibres 

 are efferent fibres as regards the cerebellum i.e., their cells of origin lie 

 in the dentate nucleus. Running upwards and forwards in the superior 



peduncle towards the mid- 

 brain they cross the middle 

 line below the corpora 

 quadrigemina, and then 

 bifurcate into ascending 

 and descending branches. 

 The ascending branches end 

 mainly in connection with 

 cells in the red nucleus, but 

 some of them pass on to 

 the optic thalamus, with 

 which cells of the red 

 nucleus are also connected. 

 The thalamus, as we have 

 seen, is in its turn exten- 

 sively connected with the 

 cerebral cortex, and the 

 red nucleus (by the efferent 

 tract of Monakow) with the 

 grey matter of the cord. 



Fig- 364. Paths of Middle Cerebellar Peduncle 

 (Mingazzini). The scheme indicates the afferent 

 and efferent paths which run through the middle 

 cerebellar peduncle, connecting cerebellum with 

 opposite side of cerebrum, a, fibre coming from 

 a cell in the nuclei pontis and going to the cere- 

 bellar cortex; b, fibre from a cell in cortex of 



The descending branches 

 of the fibres of the superior 

 peduncle, entering the re- 

 tic ular formation of the 

 pons, pass down, it is said, 

 to make connection with 

 the motor nuclei of the 

 cranial and spinal nerves. 

 The tract of Gowers, as 

 previously stated, comes 

 into relation with the su- 



opposite cerebral hemisphere making connection 



in the pons with a (a and b together constitute 



an afferent path to the cerebellum); c, a fibre 



springing from a Purkinje's cell in the cerebellar 



cortex and making connection in the pons with 



a cell d, which sends its axon to the cerebral 



cortex of the opposite side, c and d constitute 



an efferent path from cerebellum to opposite 



cerebral hemisphere; e, f, represent a path 

 , coming from the cerebellar cortex, which crosses 



the middle line in the pons, and then ascends 



till it loses itself in the formatio reticularis. 



perior peduncle, passing 



backwards along its mesial border to the worm. Since the cortex of the 

 cerebellum is linked to the dentate nucleus, the superior peduncle affords 

 an indirect connection between it and the cerebral cortex. Through 

 the restiform body afferent impulses pass up to the cerebellum. From 

 the cerebellum they may proceed to the cerebrum. So that the path by 

 the restiform body, dentate nucleus, and superior peduncle may form an 

 alternative route for afferent impressions ascending from the periphery to 

 the great brain a path broken by at least four relays of nerve-cells. 

 The cerebellar hemisphere may be connected by an efferent path through 

 the nucleus of Deiters and the descending antero-lateral tract with the 

 .motor roots of the same side. Another efferent path (from the dentate 

 nucleus) may be constituted by the fibres of the superior peduncle and 

 Monakow' s bundle. 



