A want of exercise, inducing softness in the bones, weakness in the muscles, inactivity in the digestive organs, and general debility in the nervous system: A neglect of the care of the skin, whereby the blood has not been properly purified, and the internal organs have been weakened: A violation of the laws of health, in regard to food, by eating too much, too fast, and too often; by using stimulating food and drinks; by using them too warm or too cold; and by eating that which the power of the stomach is not sufficient to digest: A neglect of the laws of health, in regard to clothing, by dressing too tight, and by wearing too little covering, in cold and damp weather, and especially by not sufficiently protecting the feet: A neglect to gain a proper supply of pure air, in sleeping apartments and schoolrooms, and too great a confinement to the house: The pursuit of exciting amusements at unseasonable hours, and the many exposures involved at such times: And lastly, sleeping by day, instead of by night, and protracting the hours of sleep, beyond the period of repose demanded for rest; thus exhausting, instead of recruiting, the energies of the system. But all the other causes, combined, probably, do not produce one half the evils, which result from a want of proper exercise. A person who keeps all the functions of the system in full play, by the active and frequent use of every muscle, especially if it be in the open air, gains a power of constitution, which can resist many evils that would follow from the other neglects and risks detailed. This being the case, there can be no subject, more important for mothers and young ladies to understand, than the influence on the health, both of body and mind, of the neglect or abuse of the muscular system. It has been shown, in the previous pages, that all the muscles have nerves and blood-vessels, running in larger trunks, or minute branches, to every portion of the body. The experiments of Sir Charles Bell and others, have developed the curious fact, that each apparently single nerve, in reality consists of two distinct portions, running together in the same covering. One portion, is the nerve of _sensation_ or _feeling_, the other, the nerve of _motion_. The nerves of sensation are those which are affected by the emotions and volitions of the mind; and the nerves of motion are those which impart moving power to the muscles. Experiments show, that, where the nerves issue from the spine, the nerve of sensation may be cut off without severing the nerve of motion, and then the parts, to which this nerve extends, lose the power of feeling, while the power of motion continues; and so, on the other hand, the nerve of motion may be divided, and, the nerve of sensation remaining uninjured, the power of feeling is retained, and the power of motion is lost.