14 TEBTEBRATE8. 



CHAPTER II. 



DIVISION I.— VERTEBRATES. 



CLASS I. — MAMMALS. 

 OEDER I. — TWO-HANDED ANIMALS. 



The Vertebrates are possessed of an internal skeleton, 

 •whicli is a perfect system of bones, corered with flesh, that serves 

 to support, strengthen, and give form to the whole structure, and 

 which also assists in enclosing the various internal organs, whose 

 action is necessary to the life and vigor of the entire system. 

 Animals of this division have a number of bones, called vertebrae, 

 joined together in the form of a long column, generally known as 

 the backbone, or vertebral column, and sometimes termed the 

 spine, surmounted by a bony case, called the cranium, or skull. 

 Through a canal, extending the whole length of the vertebral 

 column, the spinal nerve, or marrow, passes from the skull, and is 

 distributed to all parts of the body. The blood is always red, and 

 always (except under extraordinary atmospheric conditions) warmer 

 than the air or water in which the animals of this division reside. 

 The first class under this division is the 



Mammals, the females of which produce their young alive, 

 nourish them during infancy with milk from their breasts, and 

 for this reason are termed mammalia. Man, monkeys, bats, 

 quadrupeds, and whales, belong to this class. 



MAN. 



Man, as the head of the whole animal kingdom, naturally 

 ranks first in the Class Mammalia, and we shall therefore now 

 proceed to give a brief description of his organization, and subse- 

 quently point out the existing differences between his structure 

 and that of other animals of the same class. The human body 



