154 



MAMMALS 



Stomach of Sheep 



Oesophagus 



-Rumen 



Abomasum 



'Reticulum 



'Intestine 



Figure 168. — Stomach of Sheep. 



Sheep, deer, and cows chew the "cud" 

 and all have stomachs of several 

 compartments. 



used them for riding and 

 as beasts of burden." 

 The fine animals which 

 we see to-day have grad- 

 ually developed through 

 this long time from a 

 small animal about the 

 size of a fox terrier. 

 The earliest remains of 

 the feet of the ancient 

 horse show that it had 

 four toes and the remains 



of a fifth in the front foot, while the hind foot had three 

 toes and the remains of 

 a fourth. The horse and 

 the deer, which also has 

 many stages preserved 

 in the rocks, afford ex- 

 amples of the manner 

 in which some of our 

 present animals have 

 developed. This is an- 

 other good illustration 

 of evolution. 



141. Economic Importance of Mammals. — When we con- 

 sider the value to man 

 of horses, cattle, sheep, 

 pigs, and goats in this 

 country, and the value 

 of the camel and rein- 

 deer in other countries, 

 we can see the great 

 economic importance of 

 Figure 170. — Young Rabbits. mammals. Mammals 



Figure 169. — Skunk. 



