616 



NEEVOUS SYSTEM. 



FIG. 229. Inner surface of the right cerebral hem- 

 isphere (Schafer and Horsley). 

 A. S., area governing the movements of the arm i^ a-p-noval forma tVmf 



and shoulder ; Tr., area for movements of the ln g el 



trunk ; LEG, (paracentral lobule) area 



movements of the leg. 



combined with paralysis of the hypoglossal nerve ; 3, brachial monoplegia, 

 or paralysis of the opposite arm ; 4, crural monoplegia, or paralysis of the 



opposite leg ; 5, brachio-facial mono- 

 plegia, or paralysis of the arm and 

 face " (Flint's " Practice of Medi- 

 cine "). 



It is possible that there may be 

 sensory centres in the cerebral cortex, 

 but they have not been satisfactorily 

 localized, although attempts have been 

 made to limit such areas by studying 

 reflex phenomena following stimula- 

 tion of certain parts. It may be stated 



nnnirn'tal anrl 



for temporo - sphenoidal lobes, the fibres 

 from which pass through the posterior 

 third of the posterior division of the internal capsule, are specially connected 

 with sensation. 



One of the most important of the cerebral centres is the centre for 

 speech, which will be fully described after the consideration of the general 

 uses of the cerebral hemispheres. 



GENERAL USES OF THE CEREBRUM. 



The cortical gray substance of the cerebral hemispheres not only is capable 

 of generating motor impulses of the kind known as voluntary, and of receiv- 

 ing sensory impressions, including those connected with the special senses, 

 but its anatomical and physiological integrity, and its connections, especially 

 with sensory conductors, are essential to what are known as mental opera- 

 tions. The existence of the mind and the possibility of normal operations 

 of the intelligence depend upon the existence of the gray matter of the cere- 

 bral cortex and its normal physiological condition and relations. This prop- 

 osition does not imply that the mind is a force which operates through the 

 brain, or even, strictly speaking, that the brain is the seat of the intellectual 

 faculties. Mental operations involve a slight elevation of temperature and 

 slightly increase some of the excretions. It is probable, therefore, that they 

 involve changes of matter ; and these changes, if they occur, can be effected 

 only by the cells of the brain. Without defining or analyzing the intellec- 

 tual faculties or attempting to locate different faculties in special parts, it is 

 sufficient to state that certain of these faculties reside probably in that por- 

 tion of the brain which is anterior to the motor cortical zone ; that is, in the 

 frontal lobes. These lobes, as far as is known, do not present motor or sen- 

 sory areas. 



The brain and the intellectual power of man are so far superior in their 

 development to this organ and its properties in the lower animals, that some 

 philosophers have regarded the human intelligence as distinct in nature as 

 well as in degree. Although physiologists do not generally accept this prop- 



