204 PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



stimulus have been differentiated by evolution not only 

 the different forms of feeling, such as heat and cold, 

 pain, and touch proper, but also all the higher and more 

 special forms of sense. 



SECTION IX. 

 The Voice and its Organ, the Larynx. 



The voice is not one of the senses, nor is the larynx 

 a sense organ, but its close relation with the sense of 

 hearing makes this the proper place to take it up. 



There are three kinds of voice — viz., the call or cry, 

 the song, and speech. The first is the simple voice, the 

 second the harmonically modulated voice, the third the in- 

 telligently articulated 'voice. The first is common to all or 

 nearly all air-breathing vertebrates ; the second is pecul- 

 iar to man and perhaps birds; the third is characteristic 

 of man alone, although an imitated speech may be 

 taught by man to some birds. We take first 



I. SIMPLE VOICE. 



The Larynx. — Its Position and Relation. — The organ 

 of the voice is the larynx. There are two pipes leading 

 from the throat into the cavity of the trunk — the gullet 

 or oesophagus, and the windpipe or trachea. The one 

 leads into the stomach, the other into the lungs ; the one 

 is the passage for food, the other for air in breathing. 

 The trachea is in front, and may be felt with the hand, 

 for it is hard, being kept open by a series of bony or 

 cartilaginous rings, so that the air passes through with- 

 out resistance. The gullet is a soft, extensible pipe, 

 collapsed when not occupied by food. Crowning the 

 trachea and opening into the throat, just behind the root 

 of the tongue, is the larynx. Now, it will be seen (Fig. 



