The first engraving, on p. 77, (Fig. 6,) is a vertical section of the skull, and of the spinal column, or back bone, which supports the head, and through which runs the spinal cord, whence most of the nerves originate. It is a side view, and represents the head and spine, as they would appear, if they were cut through the middle, from front to back. Fig. 7, exhibits them as they would appear, if viewed from _behind_. In Fig. 6, _a_, represents the _cerebrum_, or great brain; _b_, the _cerebellum_, or little brain, which is situated directly under the great brain, at the back and lower part of the head; _c_, _d_, _e_, is the spinal marrow, which is connected with the brain at _c_, and runs through the whole length of the spinal column. This column consists, as has already been stated, of a large number of small bones, _f_, _f_, called _vertebrae_, laid one above another, and fastened together by _cartilage_, or _gristle_, _g_, between them. [Illustration: Fig. 6.] [Illustration: Fig. 7.] Between each two vertebrae, 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. [Illustration: Fig. 8.]