CHAPTER XI WORK, FATIGUE, AND HYGIENE Physiological Effects of Exercise.-Whenever work is done, energy is liberated and a disintegration of tissue takes place. This is the case when mental work is done no less than when the exercise is physical. In fact, mental labor necessitates the greater expenditure of energy. Hence, "in the study of fatigue it is the changes in the material stored in the active cells at any one time that claim attention." 1 The changes due to metabolism of the nerve-cells and consequent fatigue were first demonstrated by Hodge. He delivered some of the pioneer lectures on this subject in 1891 at the University of Wisconsin. He studied the effects of exercise upon the brain-cells of frogs, cats, honey-bees, and pigeons. By electrically stimulating the peripheral trunks of the nerves leading to the spinal ganglion of the cat, he was able to study the effects of varying amounts of exercise and rest. The nerve was stimulated for fifteen seconds, then allowed to rest forty-five seconds, the work and rest periods continuing alternately during a period of five hours. At the end of one hour the nuclei had shrunken in volume about twenty-two per cent. In some cases the shrinkage at the end of five hours was fully fifty per cent. Observations were carried on for twenty-nine hours, or twentyfour hours subsequent to the last stimulation. Complete restoration occurred within twenty-four hours. The length of time varied with different animals. Accompanying the shrinkage there was a turgescence of protoplasm, and a chemical change occurred as shown by their reaction to staining reagents. The nucleus, nucleolus, and cytoplasm of the cells themselves were 'Donaldson, Growth of the Brain, p. 311. all affected, the cytoplasm becoming vacuolated, the muscles first increasing in size and then diminishing.' Dr. Hodge studied the effects of exercise upon the nerve-cells of the pigeon, swallow, and honey-bee by examining the nerves of those killed early in the morning after a night's repose, and others of the same colony after a day's flight. He was thus enabled to discover the fatigued cells from the cortex of pigeons, those from the antennary lobes of honey-bees, from the spinal ganglia of English sparrows, and the cerebellum of swallows. The cells of the animals examined in all cases after exercise were found to be smaller and of a darker color than in fresh specimens. Other authors through subsequent experiments have corroborated many of his conclusions. Hodge also compared the cells of aged animals with those of young animals of the same species, and noted that the cells in old age present many of the symptoms of permanent fatigue. Meaning of Fatigue.-Fatigue is produced by a chemical process. Muscular action increases the oxygen absorbed and produces additional carbon dioxide. One of the principal substances produced by fatigue of muscle or nerve is lactic acid. There is a change not only in the size and microscopic appearance of the cell, but in histological appearance. It may be easily demonstrated that the toxins formed in the blood by exercise are important, if not the principal causes of fatigue. Mosso says: "They are not so much poisons as dross and impurities arising from the chemical processes of cellular life, and are normally burned up by the oxygen of the blood, destroyed in the liver, or excreted by the kidneys. If these waste products accumulate in the blood, we feel fatigued; when their amount passes the physiological limit, we become ill." Mosso and others have performed experiments to demonstrate the foregoing idea. By electrically stimulating the nervous system of a dog, tetanus is produced which modifies the blood and gives all the symptoms of fatigue. If the blood of this dog 1 Donaldson, Growth of the Brain, pp. 317-323. be injected into the veins of a fresh dog, the latter will at once become affected with all the symptoms of fatigue. Mosso cites other experiments in which he proves that temporary fatigue of muscles is a result of poisonous accumulations and not a result of the exhaustion of the substance of the muscles. The muscles of the frog's leg which have been fatigued by exercise can be restored to normal contractions by merely washing (injecting) with slightly saline water. Mosso makes a statement which will doubtless surprise many, viz.: "The blood, that mysterious liquid which Moses believed to be the seat of life and which Pythagoras called the nutriment of the soul, is not absolutely necessary to the functions of life, since we can remove it entirely and put saline solution in its place. The experiment is performed by cutting the abdominal vein and fastening therein a fine reed. Saline solution (0.75 per cent.) is then injected by means of a syringe until nothing but this clear liquid is circulating, and we obtain a frog which contains no blood. Frogs in this condition can live for a day or two, and during the first ten or twelve hours they are difficult to distinguish from normal frogs. It is not possible to perform such an experiment upon a warmblooded animal, because the nervous system cannot stand so great a disturbance of its environment." 1 A feeling of fatigue is nature's warning that katabolism is in excess of anabolism, that waste exceeds repair. It indicates a disturbed equilibrium in the machinery of life. Under normal conditions this warning is issued in time, work ceases, and repair and excess growth ensue. But in pathological cases the destruction may go on until almost too late for recuperation. Causes of Fatigue.-Bad heredity is a usual predisposing cause of fatigue. Normally developed and well-cared-for children seldom experience pathological fatigue from reasonable work. Work under such conditions induces an increased blood supply and is a prerequisite for growth. Defective eyesight or hearing, through the strain produced, are responsible for many headaches and much fatigue. An undeveloped heart, poor 1 Fatigue, p. 108. breathing apparatus, diminutive cerebral blood-vessels, insufficient food or malnutrition, are all responsible for many cases of fatigue. They are, of course, difficult of diagnosis. 66 Pathological fatigue is sometimes produced in adults by overwork, in children seldom. Dissipation of energies, intemperance, and irregularities of living are much more often the cause. Smith Baker said that injurious results frequently ascribed to 'studying too hard" can usually be traced to something else. "Much more frequently, dangerous fatigue is the result of unhealthy confinement within doors, or is owing to unwholesome shocks, and puzzlings, and confusions, and conflicts of impulses resulting from the imposition of scatterbrain notions of teaching and discipline-imposed much too fast for the child to grow to, or even to comprehend. Or, again, it may be owing to a state of chronic apprehension and fear caused by injudicious exercise of 'authority,' largely based on certain vicious interpretations of children's characteristics, moods, and tendencies." Galton wrote: "We must be on our guard against estimating a man's energy too strictly by the work he accomplishes, because it makes a great deal of difference whether he loves his work or not. A man with no interest is rapidly fagged. Prisoners are well nourished and cared for, but they cannot perform the task of an ill-fed and ill-housed laborer. Whenever they are forced to do more than their usual small amount, they show all the symptoms of being overtasked, and sicken. An army in retreat suffers in every way, while one in the advance, being full of hope, may perform prodigious feats." Vitiated air is a most prolific cause of fatigue. It is rare to find a school-building a decade old which is not absolutely inadequate in its appointments for ventilation. Engineering science is still wrestling with the problem of providing proper ventilation without undue waste of heat. Mastery seems a long way off. But even with the inadequate facilities for ventilation, rooms frequently contain fifty per cent. more pupils than 1 "Fatigue in School Children," Educational Review, 15: 35. ought to be there if the ventilation were perfect. Many teachers have dull sensibility to bad air, and even those with acute sensibility who remain in a room continuously as the poisons gradually accumulate do not notice the change readily. On the same principle that a frog may be boiled alive without feeling pain, provided the temperature is increased gradually enough, pupils may be badly poisoned from contaminated air without realizing that it is impure. The air in many school-rooms is execrable. I have visited schools in some small cities where the banks were the most conspicuous buildings, but in which the school-rooms were fairly reeking with moisture, and the odors from bodily exhalations were sickening. Dr. Amy Tanner remarks that "the air in most schools is heavy from the first half hour after school opens to the end of the day. Then the janitor locks in the bad air to be used again the next morning." 1 Ventilation of living and sleeping rooms in the homes of pupils is seldom adequate. The superstition that night air is impure, and the fear of wasting heat, cause the majority of people to sleep in rooms with absolutely no provision for the ingress of pure air and the egress of the foul. Fresh air, the one necessary luxury that might be had in abundance by the masses, is bolted and barred by them. No habit could be of greater value to children than that of breathing in deeply and slowly pure air to completely inflate the lungs several times a day. A little attention to this will develop an appetite for fresh air which will not be satisfied with foul and insufficient air. Tuberculosis would seldom develop if living-rooms were ventilated properly and if correct habits of breathing were inculcated; and many cases of this dread disease in its incipient stages could be cured by simply learning to breathe properly. The arrangement of our American courses of study is not conducive to economy of energy. Studies are not arranged in The pupil begins a subject a psychologically sequential order. like algebra, carries it for about a year, considers it "finished," and proceeds to geometry, which is "finished" with the same The Child, p. 42. |