FUNCTIONAL PARTS OF THE NERVOUS SYSTEM 



65 



superior complexity, capability, and intelligence of man. Exactly in 

 what way, however, the two facts are connected cannot be precisely told. 

 Perhaps the excess in the human brain over the brute's brain is taken up 

 in paths for the association of organic events of many sorts, this increased 

 association making possible a much larger number of actions, bodily 

 and mental, than the small-hemisphered simpler animal can perform. 



FIG. 34 



Horizontal section in the hemispheres through the ganglia: 1, 2, longitudinal fissures, former 

 between frontal lobes, latter between occipital lobes; 3, anterior part of corpus callosum; 4, fissure 

 of Sylvius; 5, island of Reil; 6, caudate nucleus of the corpus striatum; 7, the lenticular 

 nucleus of the same; 8, optic thalamus; 9, internal capsule; 10, external capsule; 11, claustrum. 

 (Dalton.) 



At any rate, the relative size of the cerebrum usually, but in a general way 

 and with many exceptions, corresponds to the complexity of the animal's 

 life. Thus, e. g., women and ants have relatively large brains. 



The hemispheres, like the nervous system in general, are composed of 



gray matter (nerve-centers) and white matter (fibers). The way in which 



these two sorts of tissue are disposed is best shown by a transverse 



horizontal section such as is illustrated in Fig. 34. Above the level of the 



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