640 The Animal Kingdom 



long snouts, short tails, and heavy build. They frequent water courses 

 and swamps. The last group of perissodactylids is that containing 

 the rhinoceroses. These huge animals live in grassy and woody areas 

 in Africa south of the Sahara and in southeastern Asia. 



Order Artiodactyla. — The members of this order are the even- 

 toed animals. They, too, are often quite large and the feet are usually 

 sheathed in a cornified hoof; however, the main axis passes between 

 the toes rather than through one as in the odd-toed forms. In general, 

 they are characterized also by their having heavy molars for chewing 

 vegetation. Two main groups are recognized : the ruminants with 

 their four-compartment stomach and the pigs and their allies. In- 

 cluded in the first group are the camels, deer, mouse deer, giraffes, 

 antelopes, bison, and the important domesticated cattle. The second 

 group includes another barnyard favorite, the domestic pig, as well 

 as its wild allies, the peccaries and boars, and the hippopotamus or 

 river hog of Africa. 



MAN AND HIS DEVELOPMENT 



From all viewpoints, man occupies a unique place in the animal 

 kingdom. He, of all animals, is able to control his environment to 

 a great extent. He is able to affect his environment so markedly due 

 to the unique development of his nervous system. Though the de- 

 velopment of the brain is foreshadowed in other vertebrates, it reaches 

 its culmination in man. 



If man were to be judged purely by structural characters, he 

 would be considered a timid creature doomed to live in thick forests 

 where he could hide from the voracious carnivores. No doubt he 

 would have to live on fruits, insects, and small mammals. Instead, 

 man has successfully invaded all but the most extreme habitats. 

 Though without wings, he outdoes the birds in the air ; without special 

 equipment for undersea breathing, he has nevertheless successfully in- 

 vaded that realm. Only the great depths of the ocean and interplanetary 

 space remain unconquered at present. Even here, he is gradually mak- 

 ing inroads. Man thus combines a very generalized physique with a 

 very specialized brain. 



Like all biological processes, the development of modern man was 

 not rapid; rather it took millions of years. Unfortunately the fossil 

 record is not clear. This may in part be due to the fact that man de- 

 veloped in the tropical forests, an area which produces but few fossils. 



