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