considering, the brachial muscle is attached about half an inch beyond
the fulcrum at the elbow, while the total length of the lever, measured
from the elbow to the palm, is 12 inches. Now, it is very evident that
the muscle or power being attached so close to the elbow, works under a
great disadvantage as regards strength. It could lift a 24-lb. weight
placed on the forearm directly over its attachment as easily as a single
pound weight placed on the palm. But, then, there is this advantage: the
1-lb. weight placed in the hand moves with twenty-four times the speed
of the 24-lb. weight situated near the elbow. What is lost in strength
is gained in speed. Whenever Nature wishes to move a light load quickly,
she employs levers of the third order.

[Illustration: Fig. 9A.--A chisel used as a lever of the third order. W,
weight; P, power; F, fulcrum.]

We have often to move our forearm very quickly, sometimes to save our
lives. The difference of one-hundredth of a second may mean life or
death to us on the face of a cliff when we clutch at a branch or jutting
rock to save a fall. The quickness of a blow we give or fend depends on
the length of our reach. A long forearm and hand are ill adapted for
lifting heavy burdens; strength is sacrificed if they are too long.
Hence, we find that the laboring peoples of the world--Europeans and
Mongolians--have usually short forearms and hands, while the peoples who
live on such bounties as Nature may provide for them have relatively
long forearms and hands.

[Illustration: Fig. 9B.--The forearm and hand as a lever of the third
order.]

Now, man differs from anthropoid apes, which are distant cousins of his,