THE NERVOUS SYSTEM 351 



over the muscles is less complete than in the higher apes and 

 Man. 



Practically nothing is known with regard to localization of 

 function in the association-zones, with the exception of the 

 localization of the centres for words ; but this exception is so 

 remarkable as to suggest that if there were any other faculties, 

 interference with which caused defects as distinct as those 

 which characterize disorders of speech, it would be found 

 that the association-zones are made up of definite centres. 

 As the evidence stands with regard to the broadest continental 

 divisions, we can merely state that it points, although not very 

 clearly, to the connection of the frontal zone, the region in 

 front of the kinsesthetic area, with ideas of personality, of other 

 zones with ideas of environment. Injury to the frontal region 

 has in certain cases resulted in the victim's losing his knowledge 

 of himself, his name, and his relation to his family. On the 

 other hand, gunshot wounds and other definite injuries have 

 in a large number of cases destroyed portions of the cortex 

 behind the forehead without causing any recognizable intellec- 

 tual change. It is quite certain that this part of the brain 

 performs no functions which are of a different, or, as it is often 

 called, higher order than those of other association-zones. It 

 has been stated that disease of the zone which intervenes beween 

 the visual and auditory areas is more likely to cause hallucina- 

 tions, disease of the frontal zone delusions. A patient fancies 

 in the one case that he sees things that are not there, or hears 

 voices when no one is speaking ; in the other case he imagines 

 himself a king ; but evidence connecting localized disease with 

 mental derangement is very scanty. The functional disturb- 

 ance which causes lunacy is usually of a general character ; 

 or, if local to begin with, it becomes general before the death 

 of the patient makes possible the examination of his brain. 



Derangements of speech throw a flood of light upon the 

 organization and manner of working of the association-zones ; 

 and, owing to the accident of the continuation of the line of 

 the carotid artery by the middle cerebral artery, which supplies 

 the speech centre, there is no other spot in the cortex so likely 

 to be thrown out of gear. A little plasma coagulates on one of 

 the cardiac valves, or about an atheromatous spot in the aorta. 

 Detached by the blood-stream, it is shot into one of the branches 



