AN AMERICAN INDIAN BRAIN 413 



the asymmetry of the brain and skull, contrasts the asjTnmetry 

 of the cranium of the higher races of man with the symmetry of 

 the apes and to a less degree of the black races. This lack of 

 symmetiy of the cranium in man is attributed to the unequal 

 development of homologous parts of the two cerebral hemi- 

 spheres, especially the great parietal and frontal association areas. 

 The greater size of the right parietal association area is given 

 as an explanation of the greater prominence of the correspond- 

 ing parietal bone and a relative shifting backward of the right 

 parietal boss, of the usually greater extent of the lateral part 

 of the left visual cortex and the retention of a more pithecoid 

 form in the left hemisphere. 



This as}Tmnetr>' is suggestive of the predominance of finictional 

 areas upon one side or the other of the brain. This has been 

 generally accepted in the predominance of the speech center 

 upon the left side in the inferior frontal g>'rus, Broca's convolu- 

 tion, and of the visual cortex in the more extensive area striata 

 and more prominent sulcus lunatus in the left hemisphere of the 

 majority of brains. Cumiingham ('02) attrilnited right-handed- 

 ness to a functional pre-eminence of the left hemisphere, al-- 

 though not supported by any constant observation of greater 

 weight or greater prominence of the so-called motor ann center, 

 of appreciable histological difference or of any regular plan of 

 asymmetrj\ The asymmetr>', although noticeable also in the 

 lower animals, "never attains the same degree as in man." A 

 deficient growth of the ascending parietal convolution (gyrus 

 post-centralis) has been found associated with the congenital 

 absence of the arm of the opposite side (Moorhead, '02). The 

 fact that this is not in the so-called motor center of the arm is 

 interesting in that it shows that the functional center does not 

 necessarily correspond to the motor center. 



The importance of this aspect of cerebral mor]iholog\' would 

 tend to compUcate the comparison of sulci and gyri, not only 

 between the two hemispheres of the one cerebrum but also be- 

 tween hemispheres of different cerebra, of individuals or of 

 races. It would be necessary, before a rational comparison could 

 be made, to establish as many points as possible of functional 

 similarity. At the present time there are few such points for 



