Fig. 7.
Between each two vertebræ, or spinal bones, there issues from the spine, on each side, a pair of nerves. The lower broad part of the spine, (see p, Fig. [1], p. [70], and Fig. [7], p. [77],) is called the sacrum; in this, are eight holes, through which the lower pairs of nerves pass off.
The nerves of the head and lungs run directly from the brain; those of all other parts of the body proceed from the spine, passing out in the manner already mentioned.
The nerves which thus proceed from the spine, branch out, like the limbs and twigs of a tree, till they extend over the whole body; and, so minutely are they divided and arranged, that a point, destitute of a nerve, cannot be found on the skin.
Some idea of the ramifications of the nerves, may be obtained by reference to the following engraving, (Fig. [8].) In this, A, A, represents the cerebrum, or great brain; B, B, the cerebellum, or little brain; (see also a, b, in Fig. [6];) C, C, represents the union of the fibres of the cerebrum; D, D, the union of the two sides of the cerebellum; E, E, E, the spinal marrow, which passes through the centre of the spine, (as seen at c, d, e, in Fig. [6];) 1, 2, 3, 4, 5, 6, branches of the nerves going to different parts of the body. As the nerves are the organs of sensation, all pain is an affection of some portion of the nerves. The health of the nerves depends very greatly on the exercise of the muscles, with which they are so intimately connected. This shows the reason why the headache, tic douloureux, diseases of the spine, and other nervous affections, are so common among American women. Their inactive habits, engender a debility of the nervous system, and these diseases follow, as the consequence.
It can be seen, by a reference to the side view, represented on page [77], (Fig. [6],) that the spine is naturally curved back and forward. When, from want of exercise, its bones are softened, and the muscles weakened, the spine acquires an improper curve, and the person becomes what is called crooked, having the neck projected forward, and, in some cases, having the back convex, where it should be concave. Probably one half of the American women have the head thus projecting forward, instead of carrying it in the natural, erect position, which is both graceful and dignified.