Physiology and Hygiene for Secondary Schools

by Francis M. Walters

Another theory is that the basilar membrane responds to all kinds of vibrations and the analysis of sound takes place in the brain.

A third view is that the filaments from the hair cells, rather than the basilar membrane, respond to the vibrations and in turn stimulate the terminations of the nerve fibers.

Fig. 155—Diagram showing how wax may plug the auditory canal and cause deafness.

Hygiene of the Ear.—The ear, being a delicate organ, is frequently injured by careless or rough treatment. The removal of the ear wax by the insertion of pointed instruments has been found to interfere with the natural method of discharge and to irritate the membrane. It should never be practiced. It is unnecessary in the healthy ear thus to cleanse the auditory canal, as the wax is passed by a natural process to where it is easily removed by a damp cloth. If the natural process is obstructed, clean warm water and a soft linen cloth may be employed in cleansing the canal, without likelihood of injury. Clean warm water may also be introduced into the auditory canal as a harmless remedy in relieving inflammation of the auditory canal and of the middle ear. Children's ears are easily injured, and it goes without saying that they should never be pulled nor boxed.

It frequently happens that a mass of wax collects in the auditory canal and closes the passage so completely as to[pg 366] cause deafness (Fig. 155). This may come about without pain and so gradually that one does not think of seeking medical aid. Such masses are easily removed by the physician, the hearing being then restored. Both for painful disturbances of the ear and for the gradual loss of hearing, the physician should be consulted.

The Hearing of School Children.—School children not infrequently have defective hearing and for this reason are slow to learn. The hearing is easily tested with a watch, the normal ear being able to hear the watch tick at a distance of at least two feet. Pupils with defective hearing should, of course, have medical attention, and in the classroom should be seated where they can hear to the best advantage.

Summary.—Sound waves constitute the external stimuli for the sensation of hearing. They consist of progressive vibratory movements of the air that originate in vibrating bodies. Through the larynx and the ear, sound waves are utilized by the body in different ways, but chiefly as a means of communication. The larynx produces sound waves which are reënforced and modified by the air passages. The ear supplies suitable conditions for the action of sound waves upon nerve cells. Both the ear and the larynx are constructed with special reference to the nature and properties of sound waves, and they illustrate the body's ability to adjust itself to, and to make use of, its physical environment.

Exercises.—1. For what different purposes are sound waves employed in the body?

2. How do sound waves originate? How are they transmitted? How do they differ from the waves on water?