166 



EVOLUTION AND GENETICS 



four toes, and they are herbivorous animals like those of the two 

 preceding orders. 



Elephants. Size and Structure. The elephants are in general 

 more primitive animals. While highly specialized in the develop- 

 ment of the ridged grinding molars and tusks, and in a number of 

 ways associated with their great bulk, they retain several distinctly 

 primitive characters, including the five functional digits. Their 

 speciaKzations are mostly associated with their size. 



The existing elephants belong to two species, the African and the 

 Indian (Fig. 90). A height of thirteen feet has been reported for 



some African individuals, and eleven feet 

 actually recorded, while a weight of six and 

 a half tons for the famous "Jumbo" is the 

 maximum on record. In these points they 

 rival all but the largest of the extinct species. 

 Lull states that a skeleton of the extinct 

 Elephas meridionalis in the Paris Museum 

 measures about fourteen feet in height at the 

 shoulder. 



Limbs. To support this enormous bulk, 

 the limbs of the elephants are developed in 

 such a way that stresses are placed on the 

 longitudinal axes of the bones. Throughout 

 the limb the bones are aligned with each other 

 in such a waj^ that at no point is the stress 

 applied ol^liquely or transversely. The result 

 is an appendage aptly characterized as pillar- 

 like. Anyone who has watched a circus parade . 

 is familiar with the peculiar shuffling straight- 

 legged gait which is the result of this structure, and with the strange 

 feet which seem little more than the blunt termination of the limbs 

 themselves, with five nail-like hoofs set along their anterior 

 margins. The skeletal strength is supplemented by this com- 

 pactness of the feet, whose digits are scarcely divergent (Fig. 91). 

 The greater part of the sole of the foot is made up of a thick pad 

 which lies behind and below the digits and receives most of the 

 weight. The hoofs, unlike those of the horse, are unimportant 

 in this respect. 



The Trunk. While in most animals with long limbs the neck 

 is correspondingly long, a compensation evident in the horse, 



^ ^ z 



3 



Fig. 91.— Forefoot, of 

 the Indian elephant, 

 anterior aspect, 

 showing the com- 

 pact skeletal struc- 

 ture. (From Lull, 

 after Flower.) 



