426 



PHYSIOLOGY 



CHAP. 



interruption, and decussate on the way to the superior cerebellar 

 peduncles. 



After complete extirpation of one-half of the cerebellum 

 which we first performed successfully on dogs March! found by 

 his method almost total degeneration of the red nucleus on the 

 opposite side and only partial degeneration of the red nucleus on 

 the same side (Fig. 226). The decussation of the superior central 

 peduncles is therefore not complete, though nearly so. 



According to the Dejerines, the red nucleus does not degenerate 



jyle 



FIG. 225. Section across the cerebellum and medulla oblongata, showing position of nuclei in 

 white matter of cerebellum. (Stilling.) i. n.rf., nucleus dentatus cerebelli ; s, band of 

 fibres derived ifrom restiform body, partly covering dentate nucleus ; s.c.p., commencement 

 of superior cerebellar peduncle ; com', com", commissural fibres crossing in median white matter. 



with unilateral cerebellar lesions that involve the cerebellar cortex 

 only, and not the dentate nuclei, which proves the origin in these 

 nuclei of the fibres that run to the red nuclei. 



Marchi's method clearly shows that the superior cerebellar 

 peduncle is largely composed of efferent fibres of cerebellar origin. 

 According to Ramon y Cajal, the axis-cylinders of the cells of 

 the dentate nucleus can be followed into this peduncle, which 

 also receives a few fibres from the cerebellar cortex. As the 

 fibres emerge from the cerebellum many of them give off large 

 collateral branches, which form a descending bundle that passes 

 through the substantia reticularis grisea, and gives fibres to the 

 nuclei of the cerebral nerves (Cajal). 



