CHAPTER XIII 



UNGULATA (continued). ARTIODACTYLA : HIPPO- 

 POTAMUSES, PIGS, AND DEER 



SUB-ORDER: ARTIODACTYLA. EVEN-TOED UNGULATES 



THE leading characteristics of this important modern group of 

 Ungulates have been delineated in the description of the Peris- 

 sodactyles. Their main feature is, of course, that they rest the 

 stress of their weight on two toes (the third and fourth of the 

 mammalian series, our "second" and "third" ringers) instead 

 of on a single toe. Therefore in the course of their development 

 they tend to become exclusively two-toed, just as the Peris- 

 sodactyles have advanced towards a one-toed condition. The 

 Artiodactyles arose very early in the development of the Un- 

 gulates, from a stock (the Condylarthra) which gave rise to the 

 Perissodactyles. The earliest known types of Artiodactyles had 

 five digits on hind and fore limbs. The digit that is equivalent 

 to our big toe very early disappeared in the hind feet of the 

 Artiodactyles. Then the thumb was lost in their hands. In 

 those days, of course, the extremity of the fore limb was much 

 more like a hand than is the case with the attenuated, highly 

 specialised limb of the modern Artiodactyle. In looking at an 

 antelope or a deer, for instance, it is hard for unlearned persons 

 to realise that from the wrist (which is falsely called the knee) 

 down to the tip of the hoof we have merely a modification of the 

 human hand. In hands and feet man is far more archaic than 

 the stag, or the horse. He has not, in fact, advanced in this 



respect much beyond the reptile. Artiodactyles that have merely 



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