so stiff that it will bear a heavy burden, and so flexible that it will
bend like rubber; yet, all the while, it transmits no shock, and even
hides a delicate nerve within that would thrill with the slightest touch.
Resting upon it, the brain is borne without a tremor; and, clinging to it,
the vital organs are carried without fear of harm.

FIG. 7.

[Illustration: B, _the first cervical vertebra, the atlas;_ A, _the
atlas, and the second cervical vertebra, the axis;_ e, _the odontoid
process;_ c, _the foramen._]

THE SKULL ARTICULATES with (is jointed to) the spine in a peculiar manner.
On the top of the upper vertebra (atlas [Footnote: Thus called because,
as, in ancient fable, the god Atlas supported the world on his shoulders,
so in the body this bone bears the head.]) are two little hollows
(_a_, _b_, Fig. 7), nicely packed and lined with the synovial
membrane, into which fit the corresponding projections on the lower part
of the skull, and thus the head can rock to and fro. The second vertebra
(axis) has a peg, _e_, which projects through a hole, _c_, in
the first.

FIG. 8.

[Illustration: _The Thorax or Chest._ a, _the sternum;_ b _to_ c, _the
true ribs;_ d _to_ h, _the false ribs;_ g, h, _the floating ribs;_ i, k,
_the dorsal vertebre._]

The surfaces of both vertebre are so smooth that they easily glide on each
other, and thus, when we move the head side wise, the atlas turns around