THE BRAIN 237 



the je_d nucleus of the crura cerebri ; thence to the other side 

 through the pedunculi cerebelli into the cerebellum. 



C. The short tracts of the spinal cord, which must be 

 regarded as reflex tracts and which run in the anterior 

 ground bundle and the Burdach column, cannot be traced 

 as separate tracts in the brain. There are also, no doubt, 

 many such pathways in the brain which connect the nerve 

 cells and serve as reflex tracts, for in the brain many reflex 

 processes take place. 



II. In the cerebral hemispheres there are still a great 

 many fibres which connect various parts of the cerebral 

 hemispheres with each other. These are: 



(1) Fibres in the corona radiata to the large ganglia of 

 the base (thalamus opticus, nucleus lenticularis, nucleus 

 candatus). 



(2) The association fibres, by which various parts of the 

 right and left half of the cerebral cortex lying on the same 

 side are connected with each other. 



(3) The commissural fibres which unite the right and left 

 half of the cerebral cortex. They pass through the corpus 

 callosum and the anterior commissure. 



The association and commissural fibres are the conducting 

 paths in psycho-physical processes which are the bases of 

 the psychical phenomena (the utilizing of the sensation in 

 formation of concepts, etc.). 



2. CENTRES IN THE MEDULLA OBLONGATA 



The medulla oblongata is a part of the central nervous 

 system which is of special importance for the maintenance 

 of life. It contains the centres for the regulation of certain 

 processes which provide for the maintenance of normal 

 metabolism (centres for respiration, circulation, and the 

 movements and secretions of the alimentary canal). The 

 great importance of these centres for the life of the animal is 

 apparent from the fact that destruction of the medulla oblon- 

 gata is immediately followed by death, while the destruction 



