CHAPTER XIV 



MAMMALS 



139. The Mammals are the most highly developed of the 

 vertebrates. They are warm blooded (the body tempera- 

 ture remaining the same in winter and summer), breathe 

 by means of lungs, and are provided with milk glands to 

 nourish the young. Most mammals are covered with 

 hair. A muscular wall (diaphragm) subdivides the body 



Figure 158. — Skeleton of 

 Dog. 



Figure 159. — Coyote. 



cavity into parts. The upper part contains the heart and 

 lungs, and the lower part contains the stomach, intestines, 

 liver, and other organs. At birth the young look like the 

 parents. 



Most mammals have two pairs of limbs. The fore limbs 

 may be variously modified for different uses, as for walk- 

 ing in animals like the horse, for climbing and for food- 



150 



