172 



B. S. Lull — Evolution of the Elephant. 



the knee and elbow are permanently bent, the upper limb-bones 

 being of the shape of an elongated S. Increasing weight 

 necessitates a straightening of the limb in order that the weight 

 may be transmitted through a vertical shaft. This is more far- 

 reaching than one would suppose, as it implies also a straight- 

 ening of the bones themselves and a shifting of the articular 

 facets from an oblique to a right angle with reference to the 

 long axis of the bone. The foot has changed its posture 



Fig. 3. American Mastodon ; after Owen. 



from the primitive plantigrade position, for the heel and wrist 

 bones are elevated above the ground and a thick pad of gristle 

 has developed beneath them in each foot, forming a cushion 

 to receive a share of the weight. The toes are not separate but 

 are imbedded in the common mass of the cylindrical foot, the 

 hoofs being represented by nails around its forward margin. 

 These may be fewer in number than the toes. 



Adaptations of the Skull and Teeth. 



Owing to the shortness of the neck and the height of the 

 head from the ground, the proboscis or trunk, which is merely 

 an elongation of the combined nose and upper lip, becomes a 

 most necessary device for securing food and water. This organ 

 is composed of a great number of muscles and so combined 

 and controlled as to give not only enormous strength but the 

 utmost delicacy of movement. The trunk terminates in one 

 (Indian) or two (African elephant) finger-like projections, with 

 which a pin can be picked up from the ground while the 

 entire organ has sufficient strength to uproot a tree. 



