Nervous Systems 



829 



fibers in the facial nerve are large; in higher vertebrates the visceral sensory 

 centers are reduced, and in birds taste sense is atrophied. The lateral line 

 is an important component of the tenth nerve from cvclostomes through 

 aquatic amphibia, the cochlea from land amphibians through mammals, 



JTerminol nerve 



Olfoctory trod 



D, Gymnuiti 



E, Equus 



Fig. 309. Dorsal views of brains of a number of vertebrates: A, Shark (Scymnus); B, 

 frog (Rana); C, alligator; D, tree shrew (Gymnura); E, horse (Equtis). From Romer, The 

 Vertebrate Body (1949). Philadelphia, W. B. Saunders. 



whereas the vestibular nerve is present in all classes. Each of these sensory 

 differences is reflected in medullary and midbrain centers. 



Figure 309 shows diagramatically the brains of representatives of various 

 classes of vertebrates. The cephalad shift in dominance parallels the anat- 

 omical development, and as the cerebellum and cerebrum become more im- 



