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accompanying sketch of the bones of the arm.]. All these distances
are equal to each other, but they are not equal to the
above-mentioned increase in the arm.
The arm between the elbow and wrist never increases by being bent or
extended.
The arm, from the shoulder to the inner joint when extended.
When the arm is extended, p n is equal to n a. And when it is
bent n a diminishes 1/6 of its length and p n does the same. The
outer elbow joint increases 1/7 when bent; and thus by being bent it
increases to the length of 2 heads. And on the inner side, by
bending, it is found that whereas the arm from where it joins the
side to the wrist, was 2 heads and a half, in bending it loses the
half head and measures only two: one from the [shoulder] joint to
the end [by the elbow], and the other to the hand.
The arm when folded will measure 2 faces up to the shoulder from the
elbow and 2 from the elbow to the insertion of the four fingers on
the palm of the hand. The length from the base of the fingers to the
elbow never alters in any position of the arm.
If the arm is extended it decreases by 1/3 of the length between b
and h; and if--being extended--it is bent, it will increase the
half of o e. [Footnote 59-61: The figure sketched in the margin is
257
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