The long bones of the pes constitute the metatarsus, which is the counterpart of the metacarpus. There are never more than five metatarsals in any normal mammal, but there may be any number less than five, down to a single one. In form and size the metatarsals of any given mammal are usually so like the metacarpals, that it requires some experience to distinguish them, but when either manus or pes is especially adapted to some particular kind of work, there may be very decided differences between metatarsals and metacarpals. For example, the burrowing forefoot of the moles is very different from the hind foot, which has undergone but little modification, and even more striking is the difference between the wing of a bat and its foot. Many other instances of a less extreme divergence might be enumerated, but when manus and pes are used only for locomotion, as in nearly all hoofed animals and many other mammals, the metacarpals and metatarsals are very similar. When there is a difference in number, it is the general rule that there are fewer metatarsals; an instance of this is found in the tapirs, which have four toes in the front foot and three in the hind. Forms which have a cannon-bone in the manus have it also in the pes, and some, like the peccaries and the jumping rodents called jerboas, have it only in the pes. The first (or inner) metatarsal, that of the great toe, or _hallux_, is sometimes opposable to the others, as in the monkeys, apes and lemurs. The word _metapodial_ is a useful general term which includes both metacarpals and metatarsals. A metapodial with its phalanges is a _digit_, a term often employed because of the ambiguity which arises in the use of the words “fingers” and “toes,” and is applicable to both fore and hind feet. Normally, the phalanges of the pes are so like those of the manus as to require no particular description; and only when the two pairs of extremities are specialized for entirely different functions, is there any notable divergence between the phalanges of manus and pes. [Illustration: FIG. 42.—Left pes of Black Bear (_Ursus americanus_), showing the plantigrade gait. _T._, tibia. _F._, fibula. _Cal._, calcaneum. _As._, astragalus. _N._, navicular. _Cn. 3_, external cuneiform. _Cb._, cuboid. _Mt. V._, fifth metatarsal.] [Illustration: FIG. 43.—Left pes of Patagonian Deer (_Hippocamelus bisulcus_), showing the unguligrade gait. _T._, tibia. _F._, lower end of fibula (malleolar bone). _Cal._, calcaneum. _As._, astragalus. _N.Cb._, coössified cuboid and navicular. _Mt. III_, _Mt. IV_, cannon-bone, formed by the coössification of the third and fourth metatarsals. _V._, Rudimentary fifth digit.]