IQ4 FUNCTIONS OF THE BRAIN. 



Thus the structural and physiological evidence indicates, beyond reasonable 

 doubt, that the vagus neuromeres (opercular and chilarial; and the five branchial 

 neuromeres of the marine arachnids have become consolidated into a single, compact 

 group, which in the vertebrates unites with the hindbrain to form the posterior 

 part of the medulla. 



VII. THE CEREBRAL HEMISPHERES. 



We have shown that in Limulus the hemispheres are primarily connected 

 with the sensory nerves of but one sense organ, the olfactory. They contain, 

 however, important secondary centers belonging to the visual and to the gustatory 

 organs. They are true cerebral centers, both in structure and function, and 

 are similar to the primitive hemispheres of vertebrates, in that they regulate or 

 control a large number of complex activities of which the several primary reflex 

 centers lie in the more remote parts of the central nervous system. They, for 

 example, exercise a tonic, or inhibitory, influence over the posterior part of the 

 brain and the cord, and they are the source of impulses that check, or maintain, or 

 coordinate, the walking and swimming movements, the leg movements in chewing, 

 and the purposeful movements of the legs in removing local irritants. 



