302 



STUDY OF BRAINS OF SIX EMINENT SCIENTISTS AND SCHOLARS. 



weight is probably less than 1 per cent, of the total brain-weight.* But if there 

 is still moi'e intricate inter-connection of nerve-cells, out of proportion as it were (by 

 means of untold numbers of association fibers), the mass of white matter must 

 necessarily be greater. So characteristic is this preponderance of white matter in the 

 brain of man, and so needful is such an elaboration and amplification of the cerebral 

 architecture to the workings of the human mind, that it is only necessary to glance at 

 the cross-sections of the brains of lower animals as compared with that of man (Fig. 

 13), while we pause to think that, after all, it is this enormous coordination of the sep- 



FlG. 77. Chart showing the cross-sectiou areas of the callosura (in square centimeters) in the brains of ten eminent 

 men (see solid black), compared with ten such of ordinary laborers, mechanics, etc. (see shaded figures). The largest cal- 

 losura (lO.Ssq. ctm. ) is that of Professor Joseph Leidy, the eminent morphologist ; the smallest (4.7 sq. ctm.) is that of 

 a laborer of ordinary intelligence. 



arate units of thought and action which constitutes the somatic basis of the highest 

 mental functions. And in the Mammalian series, as we ascend from the small-brained 

 Marsupial with few callosal fibers, intermingled with those of the dorsal or hippo- 

 campal commissure to the great neo-pallial commissure which the brain of man ex- 

 hibits, we may perceive an indication of the elaboi'ation of at least one division of the 

 great complex of association systems : I refer now to the bilateral coordinations exclu- 

 sively. But beyond the fact that the fibers of the callosum connect like regions in the 

 two hemicerebra little more is expressed, and yet every case of deficiency or disease of 

 this structure is attended by more or less profound weak-mindedness or downright 

 idiocy, not to speak of hemiparetic and other affections. And the examination of the 

 brains of these notable men, possessing large capacity for doing and tliinking much 



* Hammarberg, Thompson and Donaldson. 



