226 



NERVOUS SYSTEM OF VERTEBRATES. 



CHAPTER XV. 

 THE CEREBELLUM. 



In the most primitive existing vertebrates the cerebellar segment 

 shovi^s little or no higher organization than any segment of the 

 medulla oblongata. In man the cerebellum is, next to the cerebral 

 hemispheres, the most complex part of the brain and is connected 

 by a great number of tracts with nearly all parts of the nervous 



Decussatio veli 

 Rad. mesenc. V 

 Tectum 



Secondary gustatory nuc. 



L. lineas lateralis 



is trig. 



Tertiary 

 gustatory tract 



Fig. 112. — The relations of the cerebellum, brachium conjunctivum and gusta- 

 tory tracts in selachians {ScylUiim). Projection upon the median sagittal plane. 



system. The chief facts in the evolution of this complex organ 

 and its relationship will be dealt with in this chapter. 



In primitive vertebrates the cerebellar segment differs from 

 those following it chiefly in the absence of visceral nerve roots 

 and their primary sensory and motor nuclei. The dorsal part 



