CHAPTER XXXIX.

HYGIENE OF THE NERVOUS SYSTEM.

793. As the different organs of the system are dependent on the brain and spinal cord for efficient functional action, and as the mind and brain are closely associated during life, the former acting in strict obedience to the laws which regulate the latter, it becomes an object of primary importance in education, to discover what these laws are, that we may escape the numerous evils consequent on their violation.

794. For healthy and efficient action, the brain should be primarily sound; as this organ is subject to the same general laws as other parts of the body. If the brain of the child is free from defects at birth, and acquires no improper impressions in infancy, it will not easily become diseased in after life. But, if the brain has inherited defects, or has acquired a proneness to disease by mismanagement in early life, it will more easily yield to influences that cause diseased action. The hereditary tendency to disease is one of the most powerful causes that produce nervous and mental affections. Consequently, children have a strong tendency to the diseases from which the parents suffered.

795. When both parents have simuar defects, or have descended from tainted families, the children are usually more deeply impressed with their imperfections than when only one

793-850. Give the hygiene of the nervous system. 793. Why is it im portant to know the laws which regulate the action of the brain? 794. What is necessary that the action of the brain be healthy and efficient? What follows if the brain of the child has inherited defects? 796. What is the effect when both parents possess similar defects?

possesses the defect. This is the reason of the frequency of nervous disease and imbecility among the opulent, as intermarriages among near relations are more frequent with this class than among the poor.

Observation. Among some of the reigning families of Europe, particularly the Spanish, the folly of intermarriage among themselves is strongly illustrated. The high and noble talents that characterized their progenitors are not seen, but there is now exhibited, among their descendants, imbecility and the most revolting forms of nervous disease.

796. "Unhappily, it is not merely as a cause of disease, that hereditary predisposition is to be dreaded. The obstacles which it throws in the way of permanent recovery are even more formidable, and can never be entirely removed. Safety is to be found only in avoiding the perpetuation of the mischief."

797. "Therefore, if two persons, each naturally of excitable and delicate nervous temperament, choose to unite for life, they have themselves to blame for the concentrated influence of similar tendencies in destroying the health of their offspring, and subjecting them to all the miseries of nervous disease, madness, or melancholy." The command of God not to marry within certain degrees of consanguinity, is in accordance with the organic laws of the brain, and the wisdom of the prohibition is confirmed by observation.

Observation. The inhabitants, females particularly, of the sea-girt islands of America, are more affected with nervous diseases, than those who reside upon the mainland. The prevalence of these affections is ascribed to the frequent intermarriage of persons closely related by blood.

What is one cause of nervous disease among the higher classes? What is true of some of the reigning families of Europe? 796. Why is hereditary predisposition to be dreaded? 797. Is the prohibition of God respecting intermarriage in accordance with the organic laws of the brain? What is said of the inhabitants of the sea-girt islands of America ?

798. The brain requires a due supply of pure blood. This organ receives an unusually large supply of blood, in comparison with the rest of the body. It is estimated that one tenth of all the blood sent from the heart goes to this organ. If the arterial blood be altogether withdrawn, or a person breathes air that is filled with carbonic gas, the brain ceases its proper action, and sensibility with consciousness becomes extinct.

Illustrations. 1st. If a person lose a considerable quantity of blood, dizziness and loss of consciousness follow. This results from the brain not receiving a sufficient amount of blood to sustain its functions.

2d. When an individual descends into a well or pit that contains carbonic acid, the blood is not changed or purified in the lungs, and loss of consciousness and death soon follow.

799. The slighter variations in the state of the blood have equally sure, though less palpable effects. If its vitality is impaired by breathing an atmosphere so much vitiated as to be insufficient to produce the proper degree of oxygenation, the blood then affords an imperfect stimulus to the brain. As a necessary consequence, languor and inactivity of the mental and nervous functions ensue, and a tendency to headache, fainting, or hysteria, makes its appearance.

Observations. 1st. Let a person remain, for a time, in a crowded, ill-ventilated, hall or church, and headache or faintness is generally produced. This is caused by the action of impure blood upon the brain.

2d. If a school-teacher wishes to have his pupils, on the day of examination, appear creditably, he will be careful to have the room well ventilated. Ventilating churches might

798. Why does the brain require a due supply of pure blood? What is the effect when a person loses a considerable quantity of blood? What causes the loss of consciousness when carbonic acid is breathed? 799. What effects are produced by slight variations in the quality of the blood? From the following observations, give some of the effects of impure blood on the brain.

prevent the inattention and sleepiness that are observed during the afternoon service.

3d. In many instances, the transmission of imperfectly oxygenated blood to the brain, is an influential cause in the production of nervous disease and delicacy of constitution. The only efficient remedy for these conditions is a supply of pure blood to the brain.

800. The brain should be called into action. This organ, like the muscles, should be used, and then allowed to rest, or cease from vigorous thought. When the brain is properly called into action by moderate study, it increases in size and strength; while, on the other hand, if it is not used, the action of this organ is enfeebled, thereby diminishing the function of all parts of the body.

801. The brain, being an organized part, is subject, so far as regards exercise, to the same laws as the other organs of the body. If it is doomed to inactivity, its size diminishes, its health decays, and the mental operations and feelings, as a necessary consequence, become dull, feeble, and slow. If it is duly exercised after regular intervals of repose, the mind acquires readiness and strength. Lastly, if it is overtasked, either in the force or duration of its activity, its functions become impaired, and irritability and disease take the place of health and vigor.

802. The consequences of inadequate exercise will first be explained. We have seen that by disuse the muscles become emaciated, the bones soften, and the blood-vessels are obliterated. The brain is no exception to this general rule. It is impaired by permanent inactivity, and becomes less fit to manifest the mental powers with readiness and energy. Nor will this surprise any reflecting person, who considers that the

800. Why should the brain be called into action? 801. What is the effect if the brain is doomed to inactivity? 802. Show the consequences of disuse of the organs mentioned in preceding chapters. Does the same principle apply to the brain?

brain, as a part of the same animal system, is nourished by the same blood and regulated by the same vital laws as the muscles, bones, and arteries.

803. It is the weakening and depressing effect which is induced by the absence of the stimulus necessary for the healthy exercise of the brain, that renders solitary confinement so severe a punishment, even to the most daring minds. Keeping the above principle in view, we shall not be surprised to find that non-exercise of the brain and nervous system, or, in other words, inactivity of intellect and feeling, is a very frequent predisposing cause of every form of nervous disease.

801. For demonstrative evidence of this position, we have only to look at the numerous victims to be found among females of the middle and higher ranks, who have no calls to exertion in gaining the means of subsistence, and no objects of interest on which to exercise their mental faculties, and who, consequently, sink into a state of mental sloth and nervousness, which not only deprives them of much enjoy. ment, but subjects them to suffering, both of body and mind from the slightest causes.

805. But let the situation of such persons be changed: bring them, for instance, from the listlessness of retirement to the business and bustle of the city; give them a variety of imperative employments, and so place them in society as to supply to their cerebral organs that extent of exercise which gives health and vivacity of action, and in a few months the change produced will be surprising. Health, animation, and energy, will take the place of former insipidity and dulness.

806. An additional illustration, involving an important principle in the production of many distressing forms of disease

803. What renders solitary confinement so severe a punishment to the most daring minds? What is a predisposing cause of nervous disease? 804. In what classes do mental and nervous debility prevail? 805. How can this be counteracted? 806. Give another illustration, showing how disease of the brain is induced.