654 ANIMAL PHYSIOLOGY. 
The quality of the voice depends chiefly upon the supra- 
laryngeal cavities, 
The vocal bands of the child and of woman, being both 
shorter and lighter, account largely for the differences in pitch, 
quality, and loudness of their voices as compared with that of 
man. Success in vocalization is dependent, not only on a suit- 
able laryngeal and other mechanism, but upon the rapidity and 
completeness with which a large number of muscular and nerv- 
ous co-ordinations can be made. Speech may be either reflex 
or voluntary, but for high-class results many afferent impulses 
must determine or modify the nature of the efferent impulses, 
There is no essential difference in the mechanism of the 
speaking and singing voice; in the latter, however, the vocal 
bands take a relatively greater share than in the former, in 
which the supra-laryngeal parts are more concerned. This 
applies especially to the utterance of consonants, which may 
be classified according to the part of the above-mentioned ap- 
paratus that is more especially employed. 
It is important to remember that in all phonation, in the 
case of man at least, many parts combine to produce the result; 
so that voice-production is complex and variable in mechan- 
ism, beyond what would be inferred from the apparent sim- 
plicity of the mechanism involved; while the central nervous 
processes are, when comparison is made with phonation in 
lower animals, seen to be the most involved and important of 
the whole—a fact which the results of disease of the brain are 
well calculated to impress, inasmuch as interruptions anywhere 
among a class of cerebral connections, now known to be very ex- 
tensive, suffice to abolish voice, and especially speech-production. 
It is of great practical moment for each individual to recog- 
nize both the limit of his natural powers, especially of his 
range in singing, and at the same time to appreciate the large 
margin there is for improvement, more particularly when cul- 
tivation of the voice is commenced in childhood, and resumed 
soon after the age of puberty is attained. 
Among mammals below man the vocal bands and laryngeal 
and thoracic mechanism are very similar, but less perfectly 
and complexly co-ordinated; so that their vocalization is more 
limited in range, and their tones characterized by a quality 
which to the human ear is less agreeable. Man’s superiority 
as a speaking animal is to be traced chiefly to the special de- 
velopment of his cerebrum, both generally and in certain 
definite regions. 
