CHAPTER IX. 



ARCHITECTURE OF THE CENTRAL NERVOUS SYSTEM 

 AT MATURITY. 



Architecture at maturity Shape of skull Shape of brain Effect 

 of deformation On weight Relative development of lobes 

 Causes of change in shape Bilateral symmetry Weight of 

 right and left hemispheres Decussation Segmentation 

 Areas of spinal cord Cephalic development Brain and cord 

 in animals. 



A DESCRIPTION of the form and construction of the 

 central system, as found in the adult, must precede the 

 study of the important changes by which they have 

 been attained. Since the days when interest in such 

 matters was first aroused, the shape of the head has 

 received its share of attention, and various efforts have 

 been made to interpret it. The usual varieties among 

 normal skulls are designated as brachycephalic, or broad, 

 and dolicocephalic, or long. As a matter of experiment 

 it appears that the brachycephalic skulls are more 

 capacious, and we should expect this, perhaps, since 

 they are most nearly spherical in shape. 



In the dolicocephalic heads the lengthening does not 

 increase the volume of the cranial cavity to a degree 



sufficient to compensate for the loss consequent upon 



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