264 



POPULAR SCIENCE MONTHLY. 



Fig. 1. Vocal Cords in 

 Position for Speaking or 

 Singing. 



In the voice, as in other forms of sound, we must have, first, a 

 vibrating body to initiate the sound. This we have in the vocal cords 

 of the human body. The vibrations set up in the vocal cords (Fig. 1) 



are not due to a violent impact, as in the case 

 of the tuning fork, as this would injure the 

 delicate tissues of the sound-producing organs, 

 but are caused by the air passing between the 

 vocal cords very much as the current of air sets 

 up vibration in a reed instrument such as 

 the clarionet. In the human voice this cur- 

 rent of air is furnished by the lungs, which 

 have therefore the double duty of supplying the 

 oxygen to the blood and setting up vibrations 

 in the vocal cords for the voice. 



The chest is supplied with the most perfect mechanism for obtain- 

 ing this current of air. The main support is furnished by the ribs, 

 which give firmness to the chest. These are held together and sup- 

 ported by muscles of great strength which raise the ribs in the act 

 of inspiration. The lower part of the chest is enclosed by a broad 

 flat muscle known as the 'diaphragm,' which materially assists in giv- 

 ing its bellows-like faculty to the chest. In the act of inspiration, 

 the diaphragm is lowered and the ribs are raised, thus creating a space 

 in the lungs which is filled by the air entering through the nose and 

 throat. In expiration, however, this is reversed, the ribs being low- 

 ered and the diaphragm raised, the process being assisted by the nat- 

 ural elasticity of the lung tissue. The thorough understanding of 

 this function of the lungs should impress us with the importance of 

 not hampering their action by tight clothing or lacing, which neces- 

 sarily interferes with their freedom of action, and, by thus lowering 

 the resistance of the body, make it more liable to the entrance of 

 disease. 



The two vocal cords, whose vibration forms the essential factor in 

 the voice, are situated within the larynx, the 

 most prominent point of which is known as the 

 'Adam's apple.' The larynx has several 

 plates of cartilage which, while protecting the 

 delicate organs within, make it less liable to 

 fracture or injury than if they were made of 

 bone. By removing one of the plates of the 

 larynx, we see the edge of one of the vocal cords, 

 which consists of a narrow band of rather 

 hard tissue, whitish in color in health, and surmounted on a band of 

 muscles which not only gives it support but also enables it to adjust 

 the tension necessary for tone-formation. The vocal cords, during 



Fig. 2. Vocal Cords Dur- 

 ing Inspiration. 



