140 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



It is now well recognized that structural defects 

 or alterations in the brain entail corresponding dis- 

 turbances in the mental life. Among the most 

 marked defects of this nature are those due to 

 imperfect development of the nervous system conse- 

 quent on faults in the germ cells or on disease or 

 injury to the fetal, or infantile, brain. This arrest 

 in development gives rise to the profound disorders 

 seen in idiocy and to the somewhat less serious ones 

 of imbecility. Speaking generally, it may be said 

 that there is a fair degree of correspondence between 

 the defects of development of the cerebral rind or 

 cortex and the defect in mental capacity. The 

 brains of idiots and imbeciles are nearly always 

 below the normal weight, and in a general way defi- 

 cient brain weight means mental defect. But it is 

 only where the brain weights are very low that we 

 can admit so gross an indication as a sure sign of the 

 grade of functional capacity. It is a fact of the first 

 importance, that mental function is an expression 

 of cerebral organization rather than cerebral bulk. 

 The largest brains that have been recorded have be- 

 longed to individuals of moderate capacity. Some 

 great men have had brains of small or moderate size. 

 In those cases where a brain of abnormally large 

 size has coincided with unusual eminence, as in the 

 case of Webster and Cuvier, it is probable that the 

 individual has had the benefit of refined organiza- 

 tion as well as of great mass. 



For the study of the parallelism between structure 



