488 BONES AND MUSCLES OF THE FOOT. 



the side of the foot ; and the absence of a projecting heel 

 causes them to be very deficient in the power of keeping the 

 leg upright upon it. For it is to this projection that the 

 strong muscles of the calf of the leg are fixed, by which the 

 heel is drawn upwards or the leg drawn back upon it. Other 

 muscles at the side and back of the leg, the direction of whose 

 tendons is changed by a sort of pulley at the ankle-joint, 

 aided by the muscles of the foot itself, serve to bend the toes, 

 an action which gives great assistance in walking, running, 

 leaping, &c. And the toes are straightened by an extensor 

 muscle, which lies on the front of the leg, and of which 

 the tendon runs under an annular ligament that encircles 

 the ankle, and is then divided and spread -out to the 

 toes, over the upper surface of the foot. The great toe is 

 a very important instrument in the act of walking, since 

 much of the spring forwards is given by the bending of 

 its phalanges ; and it is provided with two flexor muscles 

 of its own. 



649. On the internal side of the foot, the bones of the 

 tarsus and metatarsus form a kind of vault or arch, which 

 serves to lodge and protect the vessels and nerves that 

 descend from the leg towards the toes. This arch further 

 serves the important purpose of deadening the shock that 

 would otherwise be experienced every time that the foot is 

 put to the ground ; for, by the elasticity of the ligaments 

 which hold together the bones that compose it, a sort of 

 spring is formed, which yields for a moment to the shock, 

 and then recovers itself. We feel the difference which this 

 makes, when we jump from a height upon our heels ; the jar 

 is then propagated directly upwards from the heel to the leg, 

 thence to the thigh, and thence to the spinal column , and if 

 it were not from the peculiar manner in which this is con- 

 structed ( 631), a severe shock of this kind might produce 

 fatal effects by concussion (or shaking) of the brain. In 

 animals which walk upon four extremities, the difference of 

 direction in which the legs are connected with the spine 

 prevents a jar from being propagated along the latter to a 

 similar degree. But in those which are destined to obtain 

 their food by sudden and extensive leaps, such as the animals 

 of the Cat tribe (the Lion, Tiger, &c.), we find an arrange- 

 ment of the bones of the foot, well adapted to diminish the 



