2 University of California PuUications in Anatomy [Vol. 2 



number, size, shape, and arrangement of their structural elements. 

 By these criteria a great number of cortical areas have been delimited, 

 some with quite sharp boundaries, others apparently presenting a 

 gradual transition to the neighboring areas. The number of these 

 areas has not as yet been determined definitely, and it is found to 

 increase as new methods of investigation are devised. The local varia- 

 tions in cortical structure force upon us the idea of diversified func- 

 tion, since everywhere else in the organism specialization in function 

 goes hand in hand with structural change; hence the conception of 

 diversified local functioning of the cortex has gained favor in the past 

 few decades. Such a conception stands, on the whole, in good accord 

 with numerous physiological experiments and clinical observations; 

 it is at present recognized by the majority of neurologists as a general 

 principle of the organization and function of the cortex (''Principle 

 of Localization"; compare Campbell 1905, G. Elliot Smith 1907, 1909, 

 Brodmann 1909, Vogt 1919, Economo-Koskinas 1925). Thus the 

 cortex appears as a composite organ comprising a great number of 

 special organs and suborgans (in the human hemisphere, according 

 to Vogt, about 200), some of them, at least, having a function of their 

 own (compare Brodmann 1909, Flechsig 1920, p. 44, and 1927, Her- 

 rick 1927; see especially the experiments of Vogt 1919, pp. 399 ff.). 

 The complexity of mental processes, however, and of their correlated 

 expressive acts in higher mammals, especially in man, suggests that the 

 more complex psychic phenomena may be compound results of the 

 activities of several cortical areas working together and probably 

 assisted by subcortical nuclear masses. If one recognizes in general 

 the close relationship between cortical structures and certain psychic 

 manifestations — and much evidence from human and comparative 

 anatomy, physiology, and pathology forces one toward such a con- 

 ception — then it is evident that any attempt to explain subjective 

 psychic phenomena in terms of natural science, in objective formulae 

 of anatomy and physiolog}^ must first define the relationship between 

 certain psychic experiences and their objective manifestations on the 

 one hand, and certain cortical localities or structures on the other. 

 The first task of research is manifestly that of analysis, before a 

 synthetic reconstruction of the mental mechanisms and their possible 

 workings can be attempted. 



How far has modem investigation succeeded in elucidating the 

 fundamental organization of the brain and in explaining its essential 

 function ? It must be admitted that, though great progress was made 



