THE VOICE AND SPEECH. 653 
It is not unlikely that, whether sexual selection has played 
any considerable part, natural selection at all events has had 
not a little to do with the preservation of those individuals 
and races that soonest and most fully developed the speech-cen- 
ters; for it is to be remembered that the principle of correlated 
growth must be taken into account. In nature generally, as in 
social life, success very frequently leads to success. As man’s 
superiority over the highest of the mammals below him is 
largely due to his possession of a speaking (and writing) faculty, 
so must we concede that racial superiority is in part traceable 
to the same cause. It is well known that the leaders among 
savage tribes are frequently effective in speech as well as strong 
of heart and arm. 
This subject is a very large, suggestive, and complex one, 
and is worthy of some thought. 
Apart from speech proper, there is a language of the face 
and body generally, in which there is much that we share with 
lower forms, especially lower mammals. Darwin, noticing this 
resemblance, regarded it as evidence strengthening .the belief 
that man is derived from lower forms. Why should the forms 
of facial expression associated with certain emotions so widely 
among different races of men be so similar to each other and 
to those which the lower animals employ, if there is not some 
community of origin? This is Darwin’s query, and he con- 
sidered, as has been stated, that the answer to be given was in 
harmony with his views of man’s origin, as based on an alto- 
gether different sort of testimony. 
The high functional development of the hand and arm in 
man, and the use of these parts in writing, are suggestive. 
Summary.—The musical tones of the voice are caused by the 
vibrations of the vocal bands, owing to the action on them of 
an expiratory blast of air from the lungs. In order that the 
bands may act effectively, they must be rendered tense and ap- 
proximated, which is accomplished by the action of the laryn- 
geal muscles, especially those attached to the arytenoid car- 
tilages. We may speak of the respiratory glottis and the 
vocalizing glottis, according as we consider the position and 
movements of the vocal bands in respiration or in phonation. 
The pitch of the voice is determined by the length and the 
tension of the vocal bands, and frequently both shortening and 
increased tensioh are combined ; perhaps we may say that al- 
tered (not necessarily increased) tension and length are always 
combined. 
