334 POPULAR SCIENCE MONTHLY. 



very long ago, there was no difference in the work done by feet and 

 hands; they were all used for walking, and were thus all, properly 

 speaking, feet. So if we want to understand our feet and hands we 

 must go back to animals which had four feet and no hands, the four 

 feet each having five toes. 



Tig. 1 is a drawing of the foot of a crocodile, which is probably 

 not unlike the earliest kind of foot. At the end of the leg bones 

 a and b we see several small bones, and, starting from these, five 

 jointed rays which in the natural position lie flat on the ground. 

 The fore feet and hind feet of the crocodile are almost exactly alike, 

 having the same work to do — i. e., helping the animal to shuffle 

 along the ground. This kind of foot is very well suited for reptiles, 

 such as crocodiles and lizards, which lead a more or less lazy life, 

 merely moving from place to place to find a patch of sunshine to lie 

 in, or a spot which the animals or insects they feed on frequent, and 

 where they can be snapped at easily. Some of these animals, it is 

 true, are capable of darting at times with lightning speed, but this 

 they seem to do by the help of their tails. 



The clumsy, shuffling way of walking on the flat of the foot has 

 been given up by most animals, but we still find it in some, such as 

 the bears, which are called plantigrades or sole-walkers because of 

 their flat-soled feet. The feet of the bear are very superior to those 

 of the crocodile, for they are armed with claws which help him to 

 hold prey and to climb trees; but his awkward, shuffling gait shows 

 pretty plainly that the method of moving on the flat sole is not the 

 best possible for running. 



A better method of running is found in most of the higher ani- 

 mals, which no longer touch the ground with the sole of the foot, but 

 only with the toes or digits, and are therefore called digitigrades or 

 toe-walkers. Fig. 2 is the foot of a doglike animal (the wolf), and 

 Fig. 3 is that of a catlike animal (the lion), and in both of these we 

 see that the part of the foot which in ourselves we call the heel does 

 not lie on the ground as in the crocodile or the bear, but is raised high 

 above it, so that the animal walks, as we have said, on its toes or 

 digits. The reason why this is a better method of running is that 

 it gives extra length to the leg. A longer leg means a longer stride 

 and greater speed. The wolves, hyenas, and foxes, which are dog- 

 like animals, and the lion, leopard, lynx, and all other catlike 

 animals are beasts of prey — that is, they eat other animals which they 

 have to hunt — and all in their turn are liable to be hunted, so they 

 need to be able to run very swiftly. Many of the catlike animals, 

 too, depend, both in attack and defense, quite as much on springing 

 as on running, and so need to be very agile. For both running and 

 springing we ourselves even use our toes and not the soles of our feet, 



