406 



LIFE ON THE EARTH 



ment. Observe how carefully the brain and the spinal cord are 

 protected, and also the thorax, which contains the heart and lungs. 



If a human skeleton is 

 procured, notice the curv- 

 ing of the spine which en- 

 ables the body to stand 

 erect. 



We have just studied 

 briefly some of the in- 

 vertebrates most closely 

 related to the welfare or 

 injury of man. Man 

 himself belongs to the 

 other great class, verte- 

 brates. The higher ani- 

 mals which furnish him 

 with the greater part of 

 his animal food also be- 

 long to this class. Al- 

 though there are great 

 variations in the struc- 

 ture of vertebrate ani- 

 mals, yet they are alike 

 in having a backbone 

 and an inner supporting 

 skeleton. 



The bony skeleton in 

 the higher forms of ani- 

 mal life consists of a 

 vertebral column, skull, 

 ribs, and appendages. 

 The main skeleton pro- 



THE NERVOUS SYSTEM or MAN 



Notice how the nerves are distributed 

 to all parts of the body. 



