Hygienic Physiology | Page 9

over and even cross the ulna.

THE WRIST, or carpus, consists of two rows of very irregular bones,
one of which articulates with the forearm; the other, with the hand.
They are placed side to side, and so firmly fastened as to admit of only
a gliding motion. This gives little play, but great strength, elasticity,
and power of resisting shocks.
THE HAND.--The metacarpal (meta, beyond; karpos, wrist), or bones
of the palm, support each a thumb or a finger. Each finger has three
bones, while the thumb has only two. The first bone of the thumb,
standing apart from the rest, enjoys a special freedom of motion, and
adds greatly to the usefulness of the hand.
FIG. 12.
[Illustration: Bones of the Hand and the Wrist.]
The first bone (Figs. 11, 12) of each finger is so attached to the
corresponding metacarpal bone as to move in several directions upon it,
but the other phalanges form hinge joints.
The fingers are named in order: the thumb, the index, the middle, the
ring, and the little finger. Their different lengths cause them to fit the
hollow of the hand when it is closed, and probably enable us more
easily to grasp objects of varying size. If the hand clasps a ball, the tips
of the fingers will be in a straight line.
The hand in its perfection belongs only to man. Its elegance of outline,
delicacy of mold, and beauty of color have made it the study of artists;
while its exquisite mobility and adaptation as a perfect instrument have
led many philosophers to attribute man's superiority even more to the
hand than to the mind. [Footnote: How constantly the hand aids us in
explaining or enforcing a thought! We affirm a fact by placing the hand
as if we would rest it firmly on a body; we deny by a gesture putting
the false or erroneous proposition away from us; we express doubt by
holding the hand suspended, as if hesitating whether to take or reject.
When we part from dear friends, or greet them again after long absence,
the hand extends toward them as if to retain, or to bring them sooner to
us. If a recital or a proposition is revolting, we reject it energetically in

gesture as in thought. In a friendly adieu we wave our good wishes to
him who is their object; but when it expresses enmity, by a brusque
movement we sever every tie. The open hand is carried backward to
express fear or horror, as well as to avoid contact; it goes forward to
meet the hand of friendship; it is raised suppliantly in prayer toward
Him from whom we hope for help; it caresses lovingly the downy
cheek of the infant, and rests on its head invoking the blessing of
Heaven,--Wonders of the Human Body.]
FIG. 13.
[Illustration: The Mechanism of the Hip Joint.]
2. THE LOWER LIMBS.--THE HIP--The thigh bone, or femur, is the
largest and necessarily the strongest in the skeleton, since at every step
it has to bear the weight of the whole body. It articulates with the hip
bone by a ball-and-socket joint. Unlike the shoulder joint, the cup here
is deep, thus affording less play, but greater strength. It fits so tightly
that the pressure of the air largely aids in keeping the bones in place.
[Footnote: In order to test this, a hole was bored through a hip bone, so
as to admit air into the socket, the thigh bone at once fell out as far as
the ligaments would permit. An experiment was also devised whereby
a suitably prepared hip joint was placed under the receiver of an air
pump. On exhausting the air, the weight of the femur caused it to drop
out of the socket, while the readmission of the air raised it to its place.
Without this arrangement, the adjacent muscles would have been
compelled to bear the additional weight of the thighbone every time it
was raised. Now the pressure of the air rids them of this unnecessary
burden, and hence they are less easily fatigued--WEBER] Indeed, when
the muscles are cut away, great force is required to detach the limbs.
THE KNEE is strengthened by the patella, or kneepan (patella_, little
dish), a chestnut-shaped bone firmly fastened over the joint.
The shin bone, or tibia, the large, triangular bone on the inner side of
the leg, articulates both with the femur and the foot by hinge joints. The
kneejoint is so made, however, as to admit of a slight rotary motion
when the limb is not extended.

The fibula (fibula, a clasp), the small, outside bone of the leg, is firmly
bound at each end to the tibia. (See Fig. 1.) It is immovable, and, as the
tibia bears the principal weight