230 STUDY OF BRAINS OF SIX EMINENT SCIENTISTS AND SCHOLARS. 



ber that the cortex of the human brain contains, in round numbers, 9,000,000,000 

 functional nerve-cells, we need not wonder at man's capacity for the manifold registra- 

 tion of sensations and the numerous transformations that characterize his mental 

 processes. 



Considering now the chief mental faculties, we find that in man's sensory apper- 

 ception of things vision and audition play the most important roles in the develop- 

 ment of intelligent thought. As Jastrow has entertainingly written in his paper : 

 " Eye-mindedness and Ear-mindedness " . . . " Man is a visual animal ; as a race we 

 are eye-minded. We regard "seeing" as believing; and we say "we see" when we 

 comprehend." 



But not all men are endowed with the same visual and visualizing powers, and 

 such variations form a basis for interesting studies. Among scientists, for example, 

 some will be found to be good visualizers, observers of concrete things with good powers 

 of memorizing and recalling their visual impressions. Others are poor visualizers, ow- 

 ing, perhaps, as Galton remarks, " to their busying themselves with abstractions and 

 generalizations, in which such a faculty would be inconvenient and thus fail to be 

 cultivated." In the brains of Joseph Leidy and Cope, hereinafter described, this dif- 

 ference between the thinker in the abstract and the observer of the concrete appears 

 to be expressed in the relative redundancy of the frontal sphere of abstract thought 

 in the one brain, and of the posterior association areas in the other. 



Next to sight, the sense of hearing is the most valuable intellectual instrument. 

 This faculty, too, varies with individuals and the " auditory type " is rarer than the 

 visual type. Beethoven and Mozart are examples of its highest development. The 

 fact that Beethoven was deaf does not invalidate the theory that his central auditory 

 associations were superiorly developed. 



The tactile and muscular sensations and the faculties of taste and smell also enter 

 into our psychic life in different degrees. Artists and others skilled in the use of their 

 hands use the tactile and muscular sense considerably in association with the visual 

 and auditory faculties. When, however, a person is deprived of sight and hearing, 

 the tactile sense may be developed to such an unusual extent as to practically recom- 

 pense the individual. We see a " tactile memory " remarkably developed in the 

 cases of Laura Bridgman, Helen Keller and others. Miss Sullivan, the teacher of 

 Miss Keller, writes that both she and Miss Keller " remember in their fingers " what 

 they have said. For Miss Keller to spell a sentence in the manual alphabet impresses 

 it on her mind just as we learn a thing from having heard, seen or uttered it many 

 times and can call back the memory of its sound or appearances. 



Thus we see how the senses help our minds to become cognizant of our environ- 



