246 AN INTRODUCTION TO ZOOLOGY. 



pair go to the nose, and provide for the sense of smell ; 

 the second go to the eyes, and provide for the sense of 

 sight ; while the eighth go to the ears, and provide for 

 the sense of hearing. The tenth nerve is called the 



!Fig. 88. — Tke most complicated form of vertebrate brain, that of Man, seen 

 in section. 



vagus, or wandering nerve, because its branches spread 

 all over the body, governing the digestive organs, 

 heart, and lungs : on account of its distribution, it 

 is also called the Pneumogastric (lung and stomach 

 nerve). In a fish's head these pairs of nerves may 

 be seen lying in order ; but in the heads of the higher 

 vertebrates, owing to the folding and overlapping of 

 the parts of the brain, the order in which the cranial 

 nerves succeed one another is more diflBcult to make 



