Nervousness that results from removable physical defects--eye strain, adenoids, indigestion, earache--will be easily detected by physical examination, and easily corrected by removing the physical defect.
Preventable nervousness due to "habit" can be quite as serious in its effects upon the mind and health as the other two forms of nervousness. Twitching the face, biting the nails, wetting the lips, blinking the eyelids, continually toying with something, being in perpetual motion and never relaxing, always changing from one thing to the next, being forever on the rush, never accomplishing anything, are common faults of both teacher and pupil. We call them mannerisms or tricks of personality. They are readily imitated by children. I once knew a young lawyer who had started life as an oyster dealer, whose power of imitation helped to make him responsive to both helpful and harmful influences. After being at the same table for two weeks with a talented man whom he admired, he acquired the latter's habit of constantly twitching his shoulder and making certain gestures. These habits in turn quickly produced a nervousness that interfered with his power to reason straight.
Nervousness is often confused with aggressiveness, initiative, confidence. "Think twice before you jump, and perhaps you won't want to jump" is a very difficult rule to follow for any one whose bodily movements are not under perfect control.
It is said that the confusion of city life causes habits of nervousness. Unfortunately no one knows whether the city children or the country children have the highest percentage of nervousness. There is a general feeling that city life causes an unwholesome degree of activity, yet one finds that those people in the city who least notice the elevated railway are those whose windows it passes. City noises irritate those who come from the country, or the city man on returning to the city from the country, but a similar irritation is felt by the city-bred man on coming to the country. Mr. Dooley's description of a night in the country with the crickets and the mosquitoes and the early birds shows that it is the unusual noise rather than the volume or variety of noises that wreck nerves. At the time of the opening of the New York schools in 1907 a newspaper published an editorial on "Where can the city child study?" showing that in New York the curriculum, the schoolhouse, and the tenements are so crowded and so noisy that study is practically impossible. Lack of sleep, lack of a quiet place in which to study at school and at home, are causes for nervousness, whether these conditions are in the city or in the country. What evidence is there that the country curriculum is less crowded or country work better adjusted to the psychological and physiological age of the country pupil? The index is there; it should be read.