October 18, 1901.] 



SCIENCE. 



609 



the occipital operculum. There is not a 

 trace of such an arrangement in the human 

 brain, and even in the anthropoid ape the 

 operculum has become greatly reduced . In- 

 deed, in man there is exactly the reverse con- 

 dition. The great size of the parietal lobe 

 is a leading human character, and it has 

 partly gained its predominance by pushing 

 backwards so as to encroach, to some ex- 

 tent, upon the territory which formerly 

 belonged to the occipital lobe.* A great 

 authority f on the cerebral surface refers to 

 this as a struggle between the two lobes for 

 surface extension of their respective domains. 

 " In the lower apes," he says, " the occipital 

 lobe proves the victor ; it bulges over the 

 parietal lobe as far as the first annectant 

 gyrus. Already in the orang, the occipital 

 operculum has suffered a great reduction ; 

 and in man the victory is on the side of 

 the parietal lobe, which presses on the occip- 

 ital lobe and begins, on its part, to overlap 

 it." Now that so much information is 

 available in regard to the localization of 

 function in the cerebral cortex, and Flechsig 

 has stimulated our curiosity in regard to 

 his great ' association areas ' in which the 

 higher intellectual powers of man are be- 

 lieved to reside, it is interesting to specu- 

 late upon the causes which have led to the 

 pushing back of the scientific frontier be- 

 tween the occipital and parietal cerebral 

 districts. 



The parietal lobe is divided into an upper 

 and a lower part by a fissure, which takes 

 an oblique course across it. Endinger,J 

 who studied the position and inclination of 

 this fissure, came to the conclusion that it 



* It is necessary to emphasize this point, because in 

 Wiedersheim's ' Structure of Man ' we are told that in 

 man there is a preponderance of the occipital lobe, 

 and that the parietal lobe is equally developed in 

 man and anthropoids. 



t Eberstaller, Wiener Medizinische Blatter, 1884, No. 

 19, p. 581. 



X ' Beitrage zur Anatomie und Embryologie, ' als 

 Festgabe Jacob Henle, 1882. 



presents easily determined difi'erences in 

 accordance with sex, race and the intel- 

 lectual capacity of the individual. He had 

 the opportunity of studying the brains of 

 quite a number of distinguished men, 

 amongst whom were Bischolf of Bonn, 

 Dollinger of Munich, Tiedemann of Heidel- 

 berg, and Liebig of Munich, and he asserts 

 that the higher the mental endowment of 

 an individual the greater is the relative ex- 

 tent of the upper part of the parietal lobe. 

 There is absolutely no foundation for this 

 sweeping assertion. When the evolution- 

 ary development of the parietal part of the 

 cerebral cortex is studied exactly the re- 

 verse condition becomes manifest. It is 

 the lower part of the parietal lobe which in 

 man, both in its early development and in 

 its after-growth, exhibits the greatest rela- 

 tive increase. Additional interest is at- 

 tached to this observation by the fact that 

 recently several independent observers have 

 fixed upon this region as one in which they 

 believe that a marked exuberance of cortical 

 growth may be noted in people of undoubted 

 genius. Thus Retzius has stated that such 

 was the case in the brains of the astronomer 

 Hugo Gylden, =^ and the mathematician 

 Sophie Kovalevsky ; f Hansemann | has 

 described a similar condition in the brain of 

 Helmholtz ; and Guszman § in the brain of 

 Rudolph Lenz, the musician. Some force 

 is likewise added to this view by Flechsig, 

 who, in a recent paper, || has called atten- 



* Eetzius, Biologis(Jie Untersuchungen, neue Folge, 

 VII., 1898, 'Das Gehirn des Astronomen Hugo 

 Gyldens. ' 



t Eetzius, Biologische Uniersuchungen, neue Folge, 

 IX., 1900, 'Das Gehirn der Mathematikerin Sonja 

 Kovalevsky.' 



j Hansemann, Zeitschrift fiir Psychologie und Fhysi- 

 ologie der Sinnesorgane, Band XX., Heft 1, 1899, 

 ' Ueber das Gehirn von Hermann v. Helmholtz.' 



^ Josef Guszman, Anatomischer Anzeiger, Band 

 XIX., Nos. 9 and 10, April, 1901, ' Beitrage zur 

 Morphologic der Gehirnoberfiache. ' 



II Flechsig, ' Neue Untersuchungen liber die 

 Markbildung in den menschlichen Grosshirnlappen, ' 

 Neurologisches Centralblatt, No. 21, 1898. 



