CHARACTERISTICS AND HABITAT. ZD 



gait, with his back slightly arched, with his body 

 barely clearing the ground, and his tail dragging upon 

 it. He runs slowly, with alternating steps, but when he 

 makes his most rapid movement, it is by the regular 

 quadruped gallop, the fore feet being raised together 

 and followed in the same manner by. the hind. An 

 ordinary dog could overtake him in a short chase. In 

 the water, however, his motions are free and graceful. 

 Water is his natural element, and he cannot trust 

 himself far from it with personal safety. The usual 

 representations of the beaver show a gradual increase 

 in the size of the body from the head to the thighs, 

 with the posterior portion much the largest. While 

 the hips are broader than the shoulders, he is the 

 largest around the centre of the abdomen, from which 

 the body tapers in both directions, but more forward 

 than back. 



Some of the details of the structural organization 

 of the beaver are of a striking character. The mus- 

 cles Avhich regulate the movements of the inferior 

 jaw are large and powerful, as may be inferred from 

 the relative size of the head, and particularly from 

 the measurements of the neck immediately behind 

 the ears. This jaw has a free horizontal movement 

 from side to side, as well as forward and back, the 

 inferior incisors moving both to the right and to the 

 left of the superior, thus enabling the beaver to mas- 

 ticate his food by a transverse and diagonal as well as 

 forward and back movement of the molars on each 

 other. Incapacity for this transverse movement of 

 the inferior jaw is made one of the characteristics of 

 the rodent order. Cuvier deduced its necessary move- 

 ments from the nature of its articulation, and from 



