The general plan of construction of the upper limb will readily be understood by means of the drawings (figs. 53 and 58, p. 122). It resembles very much that of the lower limb (see fig. 4, page 15). The one bone of the upper arm--the _humerus_--resembles the one bone of the thigh, and is jointed, above, with the shoulder-blade, which, with the collar-bone, corresponds with the pelvis. Below, it is connected with the two bones of the fore-arm--the _radius_ and _ulna_; and these correspond with the two bones of the leg. In the wrist there are eight bones, called _carpal_ bones, arranged in two rows. These are connected with five _metacarpal_ bones; and these, like the metatarsals of the foot, are jointed with the _phalanges_. Of the latter there are three in each finger; but in the thumb, as in the great toe (page 10), there are only two. [Illustration: Fig. 54.] The diagram shows how the bones of the hand are arranged in three divisions. Thus, the upper row of carpal bones (3, 4, 5) consists, practically, of three bones; the fourth (6), which is much smaller than the others, being rather an appendage to one of them than a distinct constituent of the wrist. (According to this view, the number of the wrist-bones corresponds exactly with that of the tarsal bones of the foot, viz. 7). The _outer_ of these three carpal bones (3) bears the thumb[7] and the fore-finger (I. and II.), and constitutes, with them, the outer division of the hand; the inner one (5) bears the ring-finger and the little finger (IV. and V.), and constitutes the _inner_ division of the hand; and the middle one (4) bears the middle finger (III.), and is the _middle_ division of the hand. The diagram shows, too, that the two outer bones (3 and 4), with the two outer divisions of the hand, are connected with the radius; whereas the inner bone (5) only, with the inner division of the hand, is connected with the ulna. Strictly speaking, even this bone is not directly connected with the ulna, but is separated from it, as will be shown presently, by a thick ligament. [7] In deference to custom we call the palm the _front_ of the hand; and, therefore, we speak of the thumb as the _out_er and the little finger as the _in_ner digit: though it would better accord with the ordinary position of the part, with its correspondence with the foot and with comparative anatomy, to reverse these terms.