272 EXPERIMENTAL GENERAL SCIENCE 



and causes it to settle in a new place. Dust should be removed 

 with a damp cloth and the cloth thoroughly cleaned before 

 using again. 



231. The Voice. At the top of the trachea, where it opens 

 into the throat, is a roughly triangular arrangement of car- 

 tilage, known as the larynx, in which the voice is produced. 

 In ordinary breathing, the air passes through .the larynx 

 without noise, but when we speak the edges of two flaps of 

 tissue within the larynx are caused to approach each other 

 and their vibrations in the current of air as it passes out of the 

 lungs produce the voice. The voice is reinforced by the throat 

 and back part of the head and modified into speech by the 

 nose, lips, tongue, and teeth. In childhood, the voice is 

 rather high pitched but as adult life is approached, the larynx 

 of boys increases in size and their voices become deeper and 

 heavier in consequence. 



232. Colds. As a result of chilling the body, the blood may 

 be forced into the mucous membrane lining the organs of 

 breathing and there cause an increased production of mucus 

 with its attendant coughing and spitting. One should avoid 

 drafts, wet feet, and insufficient clothing if one would escape 

 colds. While an ordinary cold may only cause temporary 

 discomfort, the inflamed membranes which accompany it 

 are favorite breeding places of various germ diseases such as 

 diphtheria, pneumonia, bronchitis, and tuberculosis. A few 

 colds, especially that form known as a cold in the head, are 

 caused by germs. One may often save himself several days 

 of illness by avoiding the vicinity of those who are coughing, 

 spitting, and sneezing. The best remedy for the ordinary cold 

 is rest and an even temperature. 



233. Expression of the Feelings. The organs of breathing 

 are also concerned in a number of actions which express our 

 feelings or show the condition of our bodies. Laughing and 

 crying are much alike and are both produced by short sharp 



