THE BRAIN 247 



indirect continuations of the cochlear nerve (through the 

 lateral fillet and the internal geniculate body to the corona 

 radiata). The nervus vestibularis is supposed to be con- 

 nected with the centres for ordinary and tactile sensations, 

 not with the auditory centre. 



(3) The visual centre lies in the cuneus, angular gyrus, 

 and occipital. Their centripetal corona radiata fibres lie in 

 the optic radiation of Gratiolet (continuation of the optic 

 tract through the external geniculate body and anterior 

 corpora quadrigemina into the corona radiata). 



(4) The olfactory centre lies in the basis of the cortex of 

 the frontal lobe, in the basal portion of the gyrus fornicatus, 

 the island of Reil, the uncus, and the inner part of tLe tem- 

 poral lobes. 



The position of the centre of taste is not yet known. 



II. Motor areas are centres by which the voluntary 

 movements are inaugurated. They lie in the same portion 

 of the cortex as the centres for tactile sensations. Their 

 centrifugal corona radiata fibres are the pyramidal tracts the 

 origin of which lies in the central convolution. In the 

 upper part of this convolution originate the motor fibres for 

 the lower extremities; in the median, those for the upper 

 extremities; and in the lower portion, those for the face. In 

 the posterior part of the lower frontal convolution, generally 

 in the left cerebral hemisphere, are situated the motor 

 centres for the muscles which function in the production of 

 voice and speech (motor speech centre). 



It is supposed that motor cells are also found in other sensory 

 areas, but this is not agreed upon by all authors. 



III. Those parts of the cerebral cortex which do not 

 belong to the sensory or motor areas form, according to a 

 new theory, the association centres. These centres func- 

 tion in the formation of concepts from the sense percepts. 

 This view is, however, rejected by many authors. 



It is supposed that the association centres differ anatomically 

 from the other centres in the following respects. The association 



