MAMMALIA 453 



quently found in vertebrates at the end of the digits takes the 

 form of a hoof. Toes are usually not more than four in number. 

 The canine teeth are small or absent. The following suborders 

 are important. 



Suborder (a) Artiodactyla (even-toed). These are ungulates 

 with toes reduced to four or two. The third and fourth toes 

 persist and bear the weight of the animal, and the second and 

 fifth, if present, may or may not touch the ground. The 

 mammae are distributed along the entire abdomen (hog) or are 

 confined to the pelvic region (ox). 



This is a splendid group containing some of man's most 

 valuable food animals. Included in it are cattle, sheep, goats, 

 antelopes, elk, deer; the giraffes; the camels and llamas; the 

 hippopotami ; and the hogs and peccaries. The ox, sheep, goat, 

 deer, and giraffe are ruminants (see p. 444). 



The chief native American forms are llama, elk, moose, 

 black-tailed deer, pronghorn antelope, Rocky Mountain goats, 

 bighorn, musk ox, and bison. The bison was formerly one of the 

 most abundant of our American ruminants. Now there are 

 only a small number of specimens in captivity and fewer still 

 wild. Most of these forms are capable of domestication, be- 

 cause of their tractable disposition and their feeding habits. 

 They are very valuable both for their hides and their food prod- 

 ucts. In addition to the flesh foods, milk and its products of 

 butter and cheese are among the most prized of human foods. 

 Milk, as are eggs, is a complete food ; that is, it contains all the 

 constituents, both organic and inorganic, necessary to support 

 growth and development, as is shown by the fact that it is the 

 sole supply of food for the young immediately after birth. 



Suborder (b) Perissodactyla (odd-toed). These are character- 

 ized by the fact that the weight of the body rests on the third or 

 middle toe, the others being more or less reduced. The stomach 

 is simple. There is no proboscis. The mammae are few and 

 confined to the pelvic region. The most common examples are 

 the horse and its allies, in which the third is the only digit, and 

 the rhinoceros, which has the second and fourth, as well. It 

 is known that the remote ancestors of the horse had a second 

 and a fourth toe where only splints occur now, and even a first 



