In making comparisons of different animals with one another, and in speaking of the relative perfection of their several organs, we must not forget that _every_ organ of every animal is perfect as regards the purpose for which it was made. But some animals are said to occupy a higher position than others, or to be superior to others, because their mechanism is more complex, and they are, thereby, enabled to perform a greater variety of functions. And, in the animal kingdom, in proportion as each function rises into prominence, and becomes well and distinctly performed, so is a special organ assigned to it, and that organ becomes more and more highly elaborated. You will not misunderstand me, then, when I say that concentration of function and perfection of structure usually go together. And, forasmuch as in the lower limbs of man there is a greater concentration of locomotive function than in any other part of any other animal, you will expect to find, in them, a greater perfection of locomotive mechanism--that is to say, a more complete combination of strength with variety, rapidity, and extent of movement--than is elsewhere to be met with. This consideration will ensure attention while I give a brief account of the anatomy of man’s lower limb, more particularly of the foot. _Structure of the Lower Limbs._ The weight of the trunk is transmitted to the knee (see fig. 4, p. 15) by a single bone--the thigh-bone. This is the longest bone in the body, measuring, on the average, nearly eighteen inches. Above, it is jointed with the haunch-bone of the pelvis at the hip-joint. From the knee two bones descend to the ankle. Of these one is much the larger, and bears the chief of the weight. The other serves to give attachment to muscles, and to strengthen the ankle-joint. It runs down on the outer side of the ankle, forming there what is called the “outer ankle;” and a process of the larger bone runs down, in like manner, on the inner side, and forms the “inner ankle.” The front and inner side of the larger bone are close under the skin. This part is called the “_shin_,” being so named perhaps from the word “chine” or edge, because the leg presents an edge along the front, to facilitate its cleaving a way through the air, water, grass, or underwood. The shin itself is not particularly tender; but the skin is a good deal exposed here, and, as it lies so near the hard bone, it is easily injured; and, when “broken,” it is often difficult to heal.