222 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



garded as one outcome of the modern doctrine of localization of 

 functions in this organ. In the beginning of the nineteenth century 

 it seems to have been the general view that those who had a high 

 degree of mental capacity might direct their activity with equal 

 success in any direction according to the training received. A man 

 who could walk fifty miles to the north, it was said, could just as 

 easily walk fifty miles to the south, and a man whose training 

 made him an eminent mathematician might with different training 

 have made an equally eminent soldier or statesman. In our day, 

 however, with our ideas of the organization of the brain cortex, 

 and our belief that different parts of this cortex may give different 

 reactions in consciousness, it seems to follow that special talents 

 are due to differences in organization of special parts of the 

 cortex. 



Subdivision of the Association Areas. — On anatomical grounds 

 Flechsig distinguishes three (or four) association areas : The frontal 

 or anterior 35, Fig. 100), which lies in front of the motor area; 

 the median or insular, — that is, the cortex of the island of Reil; 

 and the posterior, which lies back of the body feeling area, extending 

 to the occipital lobe and also laterally into the temporal lobe. 

 This area Flechsig suggests may be subdivided into a parietal area, 

 34, Fig. 100, and a temporal area, 36, Fig. 100. The greater rela- 

 tive development of these areas is one of the features distinguishing 

 the human brain from those of the lower mammals. In accordance 

 with the general conception of localization of functions Flechsig 

 suggests that these areas have different functions, — that is, take 

 different parts in the complex of mental activity. Basing his 

 views upon the nature of the association tracts connecting 

 them with the sense centers, he suggests that the posterior area 

 is concerned particularly in the organization of the experiences 

 founded upon visual and auditory sensations, and shows especial 

 development in cases of talents, such as those of the musician, 

 which rest upon these experiences. The anterior area, being in 

 closer connection with the body sense area, may possibly be espe- 

 cially concerned in the organization of experiences based upon the 

 internal sensations (bodily appetites and desires), and in al- 

 terations or defective development of this portion of the brain 

 may lie the physical explanation of mental and moral degen- 

 eracy. This general idea is borne out in a measure by histo- 

 logical studies of the brains of those who are mentally deficient 

 (amentia) or mentally deranged (dementia). It is stated* that 

 the brain in such cases shows a distinct thinning of the cortex and 

 that the maximum focus of this change is found in the prefrontal 

 lobes (anterior association area). In the case of the idiotic this 

 * Bolton, "Brain," 1903, p. 215, and 1910, p. 26. 



