_One_ of the three joints--strictly called the “ankle-joint”--is between the leg-bones and the foot-bones, that is, between the tibia and fibula, above, and the astragalus beneath. By means of it the foot may be bent or straightened upon the leg; in other words, the toes may be raised or depressed. In this movement the heel participates, being depressed when the toes are raised, and _vice versâ_. A _second_ joint is between the astragalus and the heel-bone. It permits the foot to be rolled inwards or outwards upon an antero-posterior axis; so that the sole may be turned inwards, with its inner edge upwards, or may be turned down so as to be placed flat upon the ground. A _third_ joint is between the first and second row of tarsal bones--that is, between the astragalus and the heel bone, behind, and the scaphoid and cuboid bones in front. It permits the degree of flexure of the tarsal or plantar arch to be increased or diminished. Had the several movements which are requisite for easy walking all taken place in one joint, that joint must necessarily have been very insecure; indeed, it must have been a “ball-and-socket” joint, and we should have been poised upon our feet in the state of what is called “unstable equilibrium”--a state quite incompatible with security or strength, and which would have rendered the assistance of the upper limbs essential to either standing or walking. An instance of a similar kind of mechanism to this of the joints between the foot and the leg is presented by the mode in which the head is secured upon the back-bone. We can nod the head upwards and downwards; we can turn it to either side in so free a manner that we are able to command with our eyes the whole circle in which we sit simply by the movements of the head; and we can incline the head to the right or to the left. Any of these movements may be made very quickly; and there is a separate joint or joints for each of them. Thus, the _nodding_ movement takes place between the head and the first vertebra or uppermost bone of the spine; the _turning_ of the head from side to side takes place between the first and second vertebræ, the head with the first vertebra rotating upon a pivot projected upwards from the second vertebra; and the _inclination_ of the head from side to side takes place by movements of the second vertebra upon the third, of the third upon the fourth, and so on. The result is that, although the movements are thus varied, they are free as well as rapid. Yet the head is so well poised and so strongly fixed that the neck is able to bear it all day long without fatigue; and, as though the weight of the head, which is by no means inconsiderable, were not enough for the neck, we are in the habit of selecting this as the part upon which to carry burdens. One never feels so strongly impressed with the carrying capabilities of the neck and the ankle, as when following men and women in mountain districts toiling up and down the hills under great bundles