American Woman's Home: Or, Principles of Domestic Science; / Being a Guide to the Formation and Maintenance of Economical, Healthful, Beautiful, and Christian Homes

by Catharine Esther Beecher; Harriet Beecher Stowe

The body has no power to move itself, but is a collection of instruments to be used by the mind in securing various kinds of knowledge and enjoyment. The organs through which the mind thus operates are the brain and nerves. The drawing (Fig. 50) represents them.

[Illustration: Fig. 50.]

The brain lies in the skull, and is divided into the large or upper brain, marked 1, and the small or lower brain, marked 2. From the brain runs the spinal marrow through the spine or backbone. From each side of the spine the large nerves run out into innumerable smaller branches to every portion of the body. The drawing shows only some of the larger branches. Those marked 3 run to the neck and organs of the chest; those marked 4 go to the arms; those below the arms, marked 3, go to the trunk; and those marked 5 go to the legs.

The brain and nerves consist of two kinds of nervous matter—the gray, which is supposed to be the portion that originates and controls a nervous fluid which imparts power of action; and the white, which seems to conduct this fluid to every part of the body.

The brain and nervous system are divided into distinct portions, each having different offices to perform, and each acting independently of the others; as, for example, one portion is employed by the mind in thinking, and in feeling pleasurable or painful mental emotions; another in moving the muscles; while the nerves that run to the nose, ears, eyes, tongue, hands, and surface generally, are employed in seeing, hearing, smelling, tasting, and feeling all physical sensations.

The back portion of the spinal marrow and the nerves that run from it are employed in sensation, or the sense of feeling. These nerves extend over the whole body, but are largely developed in the network of nerves in the skin. The front portion of the spinal marrow and its branches are employed in moving those muscles in all parts of the body which are controlled by the will or choice of the mind. These are called the nerves of motion.

The nerves of sensation and nerves of motion, although they start from different portions of the spine, are united in the same sheath or cover, till they terminate in the muscles. Thus, every muscle is moved by nerves of motion; while alongside of this nerve, in the same sheath, is a nerve of sensation. All the nerves of motion and sensation are connected with those portions of the brain used when we think, feel, and choose. By this arrangement the mind knows what is wanted in all parts of the body by means of the nerves of sensation, and then it acts by means of the nerves of motion.

For example, when we feel the cold air on the skin, the nerves of sensation report to the brain, and thus to the mind, that the body is growing cold. The mind thus knows that more clothing is needed, and wills to have the eyes look for it, and the hands and feet move to get it. This is done by the nerves of sight and of motion.

Next are the nerves of involuntary motion, which move all those parts of the head, face, and body that are used in breathing, and in other operations connected with it. By these we continue to breathe when asleep, and whether we will to do so or not. There are also some of the nerves of voluntary motion that are mixed with these, which enable the mind to stop respiration, or to regulate it to a certain extent. But the mind has no power to stop it for any great length of time.

There is another large and important system of nerves called the sympathetic or ganglionic system. It consists of small masses of gray and white nervous matter, that seem to be small brains with nerves running from them. These are called ganglia, and are arranged on each side of the spine, while small nerves from the spinal marrow run into them, thus uniting the sympathetic system with the nerves of the spine. These ganglia are also distributed around in various parts of the interior of the body, especially in the intestines, and all the different ganglia are connected with each other by nerves, thus making one system. It is the ganglionic system that carries on the circulation of the blood, the action of the capillaries, lymphatics, arteries, and veins, together with the work of secretion, absorption, and most of the internal working of the body, which goes forward without any knowledge or control of the mind.