SECTION XIII 

 VOICE AND SPEECH 



CHAPTER XLIII 



THE GENERAL ARRANGEMENT OF THE PHONATING 



ORGANS 



The Larynx. The production of noises and sounds by animals may 

 be accidental and intentional. Thus, the wings of an insect beating 

 the air at the rate of about 300 times in a second, produce a noise which 

 is merely a phenomenon accompanying muscular action, but animals 

 of this kind are also in possession of certain mechanisms by means 

 of which a simple communication between them is made possible. 

 The latter end they attain by the rubbing together of their hind- 

 legs or by the approximation of their mandibles. In amphibians, 

 the trachea opens anteriorly into the small laryngeal chamber which 

 is connected with the cavity of the mouth by a slit-like opening or 

 glottis. At one point, the mucous membrane lining this chamber, is 

 folded into two transverse bands, the vocal cords, which are made to 

 vibrate by the expiratory blasts of air. In reptiles, the trachea is more 

 distinctly outlined and is expanded anteriorly to form the larynx with 

 its cartilaginous walls and transverse vibrating cords. 



Curiously enough, the phonating mechanism of the higher animals 

 differs only slightly from that found in these forms. Its general 

 structural principle, as well as that of several of its minor parts, remains 

 the same. Contrary to this anatomical uniformity, the sounds of 

 these animals gradually attain a greater complexity until they acquire 

 the character of articulated sounds. Thus, vowels and consonants 

 may be distinguished in the notes of birds, which animals have in 

 general a much more extensive register than the mammals. Even- 

 tually, the sounds are joined into words and coordinated to give rise 

 to speech. In this regard, man is sharply differentiated from other 

 forms, because practically no other animal is capable of equaling 

 his register of sounds nor his faculty of sound coordination. This 

 difference, however, is not brought about by a relatively much greater 

 structural perfection of his motor apparatus, but rather by a more 

 exclusive development of the association area governing this faculty. 

 In the lower forms the production of sounds is largely a reflex phe- 

 nomenon. It becomes a complex coordinated act only in those species 

 which are in possession not only of association centers but also of a par- 

 ticular center, having to do solely with the control of the production 

 of sounds. At the present time, however, we are chiefly concerned 



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