THE BRAIN 243 



pons and in the basal ganglia there are centres which regulate the 

 body temperature (see page 181), but the existence of these cen- 

 tres has never been definitely demonstrated. 



Concerning the functions of the pineal gland nothing is 

 known. It is regarded as a rudimentary eye. 



4. FUNCTIONS OF THE CEREBRAL CORTEX 



Psycho-physical processes take place in the cells of the 

 cerebral cortex. The cerebral cortex is the seat of intelli- 

 gence. Human beings in which the cortex of the cerebral 

 hemispheres has been destroyed by disease, or animals in 

 which it has been extirpated, are stupid; they take no notice 

 of the external world, flee from no danger, do not independ- 

 ently seek their food, but they still manifest all the reflex 

 movements the centres for which are located in the lower 

 parts of the brain and spinal cord. In the animal world, the 

 cerebral hemispheres and the number of the convolutions 

 vary with the degree of intelligence. 



The question whether the various psychical processes 

 (sensations, thought, will) are localized in various definite 

 parts of the cerebral cortex or whether all the parts of the 

 cortex have the same value in psychical processes is at 

 present variously answered by different authors. In higher 

 animals (monkeys and dogs) it has been attempted to 

 localize the functions of the cerebral hemispheres in two 

 ways : either by observing the results of the stimulation of a 

 definite part of the cerebral cortex, or by studying the dis- 

 appearance of functions after removal of such a definite part. 



By the first method it has been found that in the cortex 

 there are a number of definite areas the stimulation of 

 which is always followed by the contraction of a definite 

 group of muscles. These areas, called motor areas, are, in 

 general, situated in the central convolutions. 



It is noteworthy that, under certain circumstances, stimulation 

 of the cortex is followed simultaneously by the contraction of a 

 certain group of muscles and the relaxation of the corresponding 

 antagonistic muscles. 



