THE SPEECH OF CHIMPANZEES 67 



detail that is worthy of notice. Just above the 

 opening called the glottis, which is between the 

 vocal cords, are two small sacs or ventricles. These, 

 in the ape, are larger and more flexible than in man. 

 In the act of speaking they are inflated by the air 

 passing out of the lungs through the long tube 

 called the larynx. The function of these organs 

 is to control and modify the sound by increasing 

 or decreasing the pressure of the air that is jetted 

 through this tube. They serve, at the same time, 

 as a reservoir and a gauge. 



In the louder sounds produced by the chimpanzee 

 these ventricles distend until the membrane of which 

 they are composed is held at a high tension. This 

 greatly intensifies the voice, and increases its volume. 

 It is partly due to these little sacs that the ape 

 is able to make such a loud and piercing scream. 

 But the pitch and volume of his voice cannot be due 

 to this cause alone, for the gorilla, in which these 

 ventricles are much smaller, can make a vastly 

 louder sound, unless we are mistaken about the one 

 ascribed to him. 



Although the sounds made by the chimpanzee 

 can be imitated by the human voice, they cannot 

 be expressed or represented by any system of 

 phonetic symbols in use among men. All alphabets 

 have been deduced from pictographs, and the 

 symbol that represents any given sound has no 

 reference to the organs that produced it. The few 

 rigid lines that have survived to form the alphabets 

 are conventional, and within themselves meaning- 



