FEET AND HANDS. 335 



and these animals, with whom running and springing have become 

 a constant habit, have come to use only their toes always; the heel 

 no longer touches the ground except when the animal is crouching. I 

 Now, in the foot of the crocodile (Fig. 1) it is seen that all the 

 toes are not of the same length. If animals with such feet began to 

 walk on their toes, some would not touch the ground. This, indeed, 

 is what we find in many animals, especially in those cases where 

 running is all that is required. In the feet of the dog, for instance, 



Fig. 1. Fig. 2. Fig. 3. 



only four toes touch the ground; the fifth toe, having long been less 

 used than the others, has become very small. In the hind feet, 

 which are used exclusively for running, the remains of the fifth toe 

 can be felt as a small projection under the skin, some way up the 

 back of the leg. In the fore foot of the dog, however, it is a distinct 

 toe, with a nail, which is still used for digging. 



In cats and dogs, as in the bears, claws are well developed. In 

 the dogs they are short and hard but not very sharp, and are used 

 chiefly for digging. The catlike animals, on the contrary, have very 

 sharp, hooklike claws, which are of great use in seizing and holding 

 prey. 



It is obvious that if an animal, changing still further its method 

 of walking, took to running on the tips of its nails or claws instead of 

 on its toes, it would have a still greater length of leg, and therefore 

 would be still better fitted for running swiftly. This remarkable 

 manner of running is actually found in most of the swiftest four- 

 footed animals, such as the horses and deer, and also in the cows, the 

 sheep, and the pigs, which are therefore called ungulates, ungula 

 meaning a nail. All these animals feed chiefly on grass, of which 

 they need great quantities to nourish their usually large bodies. To 

 obtain constant supplies of grass, in a wild condition, they have con- 

 tinually to roam from place to place. Their feet are admirably 

 suited for these roaming habits, and also for very swift running, 

 which is their best chance of escape from their enemies, the flesh- 

 eating wolves, tigers, etc. 



The foot of the bison (Fig. 4), in which the tips of only two toes 



