If you will examine the leg of some fowl, you can see the cartilage
that covers the ends of the bones at the joints, and the strong white
ligaments that bind the joints together.
The health, of the bones depends on the proper nourishment and exercise
of the body as much as that of any other part. When a child is feeble
and unhealthy, or when it grows up without exercise, the bones do not
become firm and hard as they are when the body is healthfully developed
by exercise. The size as well as the strength of the bones, to a certain
extent, also depend upon exercise and good health.
[Illustration: Fig. 61]
The chief supporter of the body is the spine, which consists of
twenty-four small bones, interlocked or hooked into each other, while
between them are elastic cushions of cartilage which aid in preserving
the upright, natural position. Fig. 61 shows three of the spinal bones,
hooked into each other, the dark spaces showing the disks or flat
circular plates of cartilage between them.
The spine is held in its proper position, partly by the ribs, partly
by muscles, partly by aid of the elastic disks, and partly by the close
packing of the intestines in front of it.
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