CHAPTER XXIV 

 THE VOICE AND SPEECH 



Sound as a means of communication. Because 

 sound penetrates space so rapidly and is so easily pro- 

 duced, it is used by many kinds of animals as a means 

 of communication. The sounds thus used range from 

 the shrilling of insects through various inarticulate coo- 

 ings, gruntings and squealings up to the articulate 

 speech of human beings. The mechanism by which these 

 sounds are produced varies markedly in different ani- 

 mals. Many insects, as the katydid, use their wings 

 by rubbing them against the sides of their bodies. 

 Others, as the locust and cricket, use their legs in a 

 similar fashion. Most of the higher animals, however, 

 including the birds, use for this purpose the air cur- 

 rents produced by respiration. For this, they have a 

 special organ developed in the trachea for the produc- 

 tion of voice, the larynx. 



Larynx and vocal cords. The larynx is situated in 

 the upper part of the trachea, and, as we have seen, is 

 a hollow tube or box made up of several pieces of 

 cartilage, through which the air passes on its way to 

 and from the lungs. Across the larynx are stretched 

 two membranes known as vocal cords. The vocal cords 

 are attached in front and at the sides to the larynx. 

 At the back, they are attached to two small pieces of 

 cartilage which are freely moved by muscles. For the 

 production of voice, these pieces of cartilage swing al- 



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