The human foot and the human hand

by George Murray Humphry

THE HUMAN HAND.

THE great characteristic of the Hand, as distinguished from the Foot, is the mobility of the first digit, or thumb. Accordingly when this digit stands out apart from the others, and can be moved independently of them, so as to be more or less completely opposed to them, in the upper or Mammalian Class of animals, at least, we call the member a Hand. When this digit is absent, or is fixed in the same manner as the others, which is the case in each of the four limbs of Quadrupeds, we call the member a Foot. In Monkeys, or in most of them, the thumb is present and is separate and moveable in each of the four limbs; and these animals are, therefore, called “quadrumanous” or “four-handed.” Man, having the moveable thumb upon each of the two upper limbs only, is “bimanous” or “two-handed.” By this peculiarity, perhaps more definitely than by any other, he is distinguished in structure from all the rest of the animal series; and naturalists have, accordingly, given the epithet “Bimanous” to the class in which he is placed, and in which he stands alone.

The hand is the executive or essential part of the upper limb. Without it the limb would be almost useless. The whole limb is, therefore, so made as to give play and strength to the hand; and, in ever so brief a description of the hand, it is necessary, even more than in the case of the foot, to give some idea of the manner in which the other parts of the limb are constructed, and to dwell a little upon such points as have relation to its movements.

Fig. [53].

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.

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.

You frequently hear ignorant persons (and the greater number of persons are lamentably ignorant of the structure of their own body) speaking of the small bones of the shoulder, or the small bones of the elbow. You may think this a matter of no importance, and that it does not concern you and people generally to have any knowledge of human anatomy. But I will tell you what is very often happening, and will leave you to judge whether such complete ignorance on this subject is not attended with some practical disadvantage. A man meets with an injury, falls and hurts his shoulder. The immediate effects of the injury subside; but he does not quickly recover the use of the part; he still cannot raise his elbow, or put his hand upon his head, or put it behind him. Soon he begins to think that something more is wrong than has been suspected; and the notion creeps over his mind, and gradually takes possession of it, that some small bone is displaced. Not content with the assurances of his medical man, he resorts to a quack, called a “bone-setter.” The latter, taking advantage of the popular fallacy, gratifies the patient with the information that his fears are correct, affirms that “a small bone is out,” and proceeds forthwith to employ the requisite forcible measures for putting the said “small bone” in. I need not say with what result. Every year, in this civilized country, many persons are maimed for life by these attempts to put imaginary small bones in. I beg you, therefore, particularly to observe that there is no small bone either at the shoulder or at the elbow. The only small bones are at the wrist; and these are so well fitted to one another, and so firmly bound together, that nothing short of a crushing force suffices to displace them. This remark respecting the small bones of the wrist is true of nearly all the small bones in other parts of the body. So that, in fact, small bones are very rarely dislocated; and when you hear it asserted that a small bone is out, you may pretty confidently conclude that the speaker does not know what he is talking about.