THE CENTRAL NERVOUS SYSTEM 



779 



(2) A great afferent or sensory path by which some at least 

 of the impulses carried up through the posterior roots of the 

 spinal nerves, after passing through various relays of nerve-cells, 

 reach the cortex of the cerebellum ; or the upper portions of 

 the central grey tube, the corpora quadrigemina and optic 

 thalamus ; or, finally (through the tegmentum and the posterior 

 limb of the internal 

 capsule behind the 

 motor fibres), the cere- 

 bral cortex itself. 



The efferent pyra- 

 midal path from the 

 cortex to the periphery 

 is broken by at most 

 two relays of nerve- 

 cells those inter- 

 calated cells to which 



reference has already Fix. 328. PATHS OF MIDDLE CEREBELLAR 



PEDUNCLE (MINGAZZINI). 



The scheme indicates the afferent and efferent 

 paths which run through the middle cerebellar 

 peduncle, connecting the cerebellum with the 

 opposite side of the cerebrum, a, fibre coming 

 from a cell in the nuclei pontis and going to the 

 cerebellar cortex ; b, fibre from a cell in the 

 cortex of the opposite cerebral hemisphere 

 making connection in the pons with a (a and 6 

 together constitute an afferent path to the cere- 

 bellum) ; c, a fibre springing from a Purkinje's 

 cell in the cerebellar cortex and making connec- 

 tion 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 the cere- 

 bellum to the 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. 



been made (p. 775), if 

 they really exist, and 

 the motor cells of the 

 anterior horn. The 

 afferent path to the 

 cerebral cortex is in- 

 terrupted by at least 

 three relays with 

 axons of considerable 

 length. One of the 

 cells is situated in the 

 ganglion on the pos- 

 terior root, another 

 in the medulla oblon- 

 gata, a third in the 



optic thalamus ; and 

 on some of the routes another, or even more than one, is inter- 

 calated between the medulla and the cortex. 



Connections of the Grey Matter of the Cerebellum with the 

 Periphery and other Parts of the Central Nervous System. 



Numerous as are the nervous ties of the cerebral cortex, those of the 

 grey matter of the cerebellum are, in proportion to its mass, still 

 more extensive, particularly as regards afferent fibres, and perhaps 

 not less important. 



Speaking broadly, we may say that the restiform body or inferior 

 peduncle connects chiefly the dentate nucleus and the grey matter 

 of the worm with the spinal cord and medulla oblongata, and 

 through them with the periphery. The fibres which it receives from 

 the direct cerebellar tract (dorsal spino-cerebellar tract) of its own 

 side it carries to the worm. These fibres occupy the outer portion 



