THE SENSES 



interval becomes a little wider during inspiration and a little 

 narrower during expiration. 



2. In Vocalization. The production of sound in the larynx 

 involves an approximation of the cords and an increase in 

 their tension. They are made more nearly parallel by the 

 approach of the arytenoids to each other, and the rima glot- 

 tidis assumes the shape of a mere chink. The tenser the 

 cords, the higher the note produced ; usually also the closer 

 the cords are brought together, the higher the note. The 

 range of the voice depends principally on the degree of ten- 

 sion which the cord can be made to assume. 



Varieties of Vocal Sounds. These are mainly (i) mo- 

 notonous, (2) transitional, (3) musical. 



1. In monotonous sounds the notes have all nearly the 

 same pitch, as in reading. 



2. In transitional sounds there is a gradual change in the 

 tension and approximation of the cords, so that the notes be- 

 come successively higher or lower, as in the howling of a 

 dog. 



3. In musical sounds the vocal cords have a definite num- 

 ber of vibrations for each successive note a number corres- 

 ponding to the production of that note in the musical scale. 



The range of the average human voice is from one to 

 three octaves. The highest and lowest notes of females are 

 about one octave higher than the corresponding notes of 

 males. The chief difference between male and female 

 voices is, therefore, one of pitch; but they also differ materi- 

 ally in tone. The difference in pitch is a result of the differ- 

 ent length, and therefore the different rate of vibration, of 

 the cords in the two sexes. The female cords are about 

 two-thirds the length of the male. 



Before puberty the male larynx resembles the female, but 

 at that period the alae of the thyroid becomes more promi- 

 nent in the male and the cords increase in length, thus ac- 

 counting for the change of voice. 



In old age control of the musculature of the larynx is 



