Upon a general survey of the structure and form of the foot, we are struck with the differ ence between this organ in man and in all other animals. The most striking peculiarities con sist in the great breadth of the foot, its short ness in proportion to the leg, the large size of the bones of the tarsus, the relative shortness and smallness of the four outer toes, and the great size of the inner one, the great strength of the calcaneum, and lastly, in those arches produced by the arrangement and form of the tarsal and metatarsal bones. The only animal that nearly approaches to the form of man, the monkey, yet differs from him in all these points. Its foot is narrower and longer in proportion to the leg, its tarsal hones are smaller, its four outer toes are long like the fingers, while the first is small, and separated from the rest. The calcaneum is relatively small, and inclines upwards at its posterior projection, while the peculiarities already spe cified necessarily occasion that the arches of the foot are much less distinct than in man. Indeed, in supporting itself erect, the monkey rests very much on the outer side of the foot, probably on this account. In all other animals these differences are still more marked. What now can be more evident or more beautiful than the design manifested in this simple arrangement of the foot I Man is physically as well as morally intended to carry him self erect. The breadth of his base was ne cessary for his continued support ; the strength of it is called for on account of the great weight which erect progression throws upon it. Its arches were essential not only to give lodgment and defence to the vessels and nerves of the plantar region, but, by the peculiarity of their construction, to admit of a certain degree of elastic yielding, which greatly dimi nishes the shocks from violent efforts in leaping, running, &c. The shortness of the toes, aug mented by the depth of the webs, shows that pre hension forms no part of the design of the foot, while the size of the first toe, and its connexion with the others, points it out as the principal instrument of progression, to which the rest are auxiliary. The analogies between the foot and the hand are striking; they have the same general arrangement of bones and muscles, and even the arteries and nerves, the joints and ligaments, are in many respects similar, but in the particulars just mentioned the dif ference is strikingly obvious and important, and just in these respects it is that the feet of the Quadrumana also differ from those of man, showing a difference in their intended action, the erect position, at the utmost being only occasional, not being the natural habit, but the foot being prepared and adapted for grasping and clinging, for which the human foot is quite unfit.
The construction of the arches of the foot requires a few words. They are two in number,
a transverse and a longitudinal one. The latter of these is principally found along the inner edge of the foot, and as we pass towards the outer side the longitudinal arch gradually shortens and becomes more flattened, until at the outer side the arch is entirely lost, the bones of the tarsus and metatarsus resting through their whole length upon the ground. This is to a certain degree necessary from the construction of the toes, these being weaker and shorter, as well as their metatarsal bones, as they are further from the great toe; as their strength therefore diminishes, the corresponding part of the arch is shortened and flattened, and, consequently, less strain is thrown upon them, until, at the line of the little toe, the arch is obliterated, and what weight is resting here comes at once upon the ground. But from this construction it follows that the longest and the highest line of this arch falls upon the strongest metatarsal bone and longest toe, and that whatever yielding there is occurring in the entire longitudinal arch is greatest in this part of it. This is, indeed, proved by the fact that the length of the foot in a sound state is in creased in the line of the great toe to the extent of several lines, by resting the weight of the body upon the foot, whereas it is not at all increased in the line of the little toe. When, therefore, the arch yields to the superincumbent pressure, it does su chiefly along the inner side, and the foot is thus, to a certain degree, twisted, the inner malleolus approached nearer to the ground, while the outer is very little, if at all, lowered. This explains to us the reason of the scaphoid and inner cuneiform bones projecting as they do in the flat foot, and of the pain ex perienced on the inner side of the foot in the same deformity in all efforts to raise the heel in walking. It may also in some degree account for the fact of the more frequent occurrence of dislocation of the tibia at the ankle-joint in wards than outwards, the arch of the foot yielding first to the force of the accident on the inner side, and thus tilting the whole ankle joint inwards. The utility in walking of the form and relation of the various parts of the foot now mentioned is readily seen when we unite the consideration of the structure of this arch with the combined action of the gastro enemii upon the heel, and of the peroneus longus upon the outer side of the foot. The united action of these muscles throws and sustains the whole weight upon the strongest and most elastic part.
Whatever has been said of the utility of the longitudinal arch applies equally to the trans 'verse arch, which is supplementary and auxiliary to the former in all its uses.
(A. T. S. Dodd.)