THE CEREBELLAR CORTEX 41 



THE CORPUS DENTATUM OF THE CEREBELLUM 



Deep within the cerebellum, surrounded on all sides by white fibres, there lies, in each 

 hemisphere, a thin, convoluted mass of gray matter, known as the corpus dentatum. This is 

 made up of nerve cells and of their branches, and appears to be in close connection with the 

 white matter around it. In fact, many fibres in all the peduncles appear to terminate in or 

 to arise from the corpus dentatum, though the chief mass of fibres issuing from it pass into 

 the superior cerebellar peduncle. 



Plate XX. shows the appearance of a portion of this body; the convolutions of the gray 

 matter, with the bundles of nerve fibres sweeping around them, or penetrating into them ; 

 the large polygonal cells which lie near the surface of one convolution ; their dendrites coming 

 off entirely upon the inner side of the cell, i.e. upon the side toward the cavity of the con- 

 volution and branching in every direction ; and the plexus of nerve fibres everywhere present 

 throughout the gray matter. The size of the cells is about 35 /t. They are known to have 

 a neuraxon, but it has not been possible to follow it out or to determine its direction or 

 terminations by the Golgi method. The method of degeneration, however, proves that the chief 

 destination is the red nuclei of the tegmentum, the majority of the fibres decussating with those 

 of the opposite side. It is probable that a part of the fine plexus of nerve fibres in the 

 corpus dentatum consists of terminal filaments of neuraxons coming to this body from a distance, 

 chiefly from the red nuclei of the tegmentum and from the spinal cord. 



There are several small groups of cells forming nuclei within the cerebellum, lying in the 

 portion covering the roof of the fourth ventricle, and hence known as the tegmental nuclei, 

 the cells of which resemble those of the corpus dentatum. 



It may be added that the olivary bodies and the interolivary nuclei of the medulla are 

 composed of cells of identical appearance and structure with those of the corpus dentatum. 



THE CONNECTIONS OF THE CEREBELLUM 



The origin, course, and termination of the various tracts of fibres which enter and leave 

 the cerebellum and which make up the white matter beneath its cortex may best be under- 

 stood by the aid of the diagram (Fig. 7). 



The cerebellum is connected with the other parts of the nervous system by three 

 peduncles. 



I. The inferior peduncle of the cerebellum contains fibres which come from 'several 

 sources, viz. : 



