ed to the margin
of the ribs. 8, 10, The two fleshy pillars of the diaphragm, which are
attached to the third and fourth lumbar vertebrae. 9, The spinal column.
11, The opening for the passage of the aorta. 12, The opening for the
oesophagus. 13, The opening for the ascending vena cava, or vein.]

_Observation._ The diaphragm may be compared to an inverted basin, its
bottom being turned upward into the thorax, while its edge corresponds
with the outline of the edges of the lower ribs and sternum. Its
concavity is directed toward the abdomen, and thus, this cavity is
very much enlarged at the expense of that of the chest, which is
diminished to an equal extent.

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159. Describe the diaphragm. What vessels penetrate this muscular
septum?

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160. "The motions of the fingers do not merely result from the action
of the large muscles which lie on the fore-arm, these being concerned
more especially in the stronger actions of the hands. The finer and
more delicate movements of the fingers are performed by small muscles
situated in the palm and between the bones of the hand, and by which
the fingers are expanded and moved in all directions with wonderful
rapidity."

[Illustration: Fig. 43. A front view of the superficial layer of muscles
of the fore-arm. 5, The flexor carpi radialis muscle. 6, The palmaris
longus muscle. 7, One of the fasciculi of the flexor sublimis digitorum
muscle, (the rest of the muscle is seen beneath the tendons of the
pintails longus.) 8, The flexor carpi ulnaris muscle. 9, The palmar
fascia. 11, The abductor pollicis muscle. 12, One portion of the flexor
orevis pollicis muscle. 13, The supinator longus muscle. 14, The extensor
ossis metacarpi, and extensor primi internodii pollicis muscles, curving
around the lower border of the fore-arm. 15, The anterior portion of the
annular ligament, which binds the tendons in their places.

_Practical Explanation._ The muscles 5, 6, 8, bend the wrist on the bones
of the fore-arm. The muscle 7 bends the second range of finger-bones on
the first. The muscle 11 draws the thumb from the fingers. The muscle 12
flexes the thumb. The muscle 13 turns the palm of the hand upward. The
muscles 8, 13, 14, move the hand laterally.]

[Illustration: Fig. 44. A back view of the superficial layer of muscles
of the fore-arm. 5, The extensor carpi radialis longior muscle. 6, The
extensor carpi radialis brevior muscle. 7, T