CH. XLVIII.] INTELLECTUAL AREAS OF BRAIN 691 



essentially motor in function. Naturally, he does not deny that it 

 has connections with sensory fibres, but he considers it incorrect to 

 speak of the area as a sensory one. He has produced injuries of the 

 area without obtaining any loss of sensation, and in testing the 

 sensations of his monkeys employs the method of stroking the skin, 

 which he regards as more trustworthy than Schiff s clip test. The 

 sensory disturbances observed by others he regards as due to general 

 disturbance of the brain produced by the severity of the operation. 



On referring once more to the maps of the brain, it will be seen 

 that there are many blanks ; one of these is in the anterior part of 

 the frontal region. Extirpation or stimulation of this part of the 

 brain in animals produces but little result. The large size of this 

 portion of the brain is very distinctive of the human brain, and it 

 has therefore been supposed that here is the seat of the higher intel- 

 lectual faculties. Such a question is obviously very olimcult to 

 answer by experiments on animals. Both experimental physiology 

 and pathology have localised the sensory areas (and sensations are 

 the materials for intellect) either within or behind the Eolandic area, 

 but this does not necessarily mean that the frontal convolutions have 

 nothing to do with intellectual functions. The celebrated American 

 crowbar accident is generally quoted as a proof to the contrary; 

 owing to the premature explosion of a charge of dynamite in one of 

 the American mines a crowbar was sent through the frontal region of 

 the foreman's head, removing the anterior part of his brain. He is 

 usually stated to have subsequently returned to his work, without 

 any noteworthy symptoms. Eecent examination of the records of 

 the case has shown that this is not correct ; when he returned to 

 work he was practically useless, having lost just those higher 

 functions which are so important in the superintendence of other 

 people. Mott's observations on lunatics show that this region is 

 important for intellectual operations, though not so important as the 

 parietal association area behind the Eolandic area; the greater the 

 intellectual development, the larger and more convoluted does this 

 parietal region become. 



The association fibres have been the subject of special study by 

 Flechsig, who has shown that in the development of the brain these 

 are the last to become myelinated ; white fibres do not become fully 

 functional until they receive their medullary sheath. This coincides 

 with the well-known fact that association of ideas is the last phase in 

 the psychical development of the child. It has been shown that the 

 frontal convolutions are connected by important association tracts 

 with the more posterior regions of the brain, and that there is there- 

 fore no difficulty in understanding that the frontal convolutions play 

 the part of a centre for the association of ideas, or in other words for 

 intellectual operations. 



