1470 THE VOICE. [BOOK in. 



produce the same kind of voice by different dispositions of the 

 larynx. In any case the subject is one of extreme complexity, and 

 we have ventured to dwell on it, even so long as we have, because 

 it affords a striking illustration of what we have more than once 

 insisted upon, the complicated character so often belonging to the 

 muscular contractions by which the animal body gains its ends, and 

 the delicately adjusted coordination of efferent nervous impulses 

 needed to secure for the effort a complete success. We have so re- 

 peatedly, in previous parts of this work, insisted on the importance 

 of afferent impulses to the coordination of complex movements that 

 it is hardly necessary here to do more than to point out that the 

 connection of the use of the voice with auditory sensations affords 

 striking instances of the truth of what we have insisted upon. 

 Auditory sensations are at least as important for the proper 

 management of the voice as are visual sensations for the move- 

 ments of the eyes, and more important than are visual sensations 

 for the movements of the body and limbs. Indeed they are in a 

 way essential to the very utterance of the voice ; the dumbness 

 which is so conspicuous a concomitant of congenital deafness is 

 in most cases due not to deficiency in the muscular apparatus or 

 even in the nervous mechanism on what we may call its motor side, 

 but to the lack of afferent impulses from the auditory nerve. And 

 in popular language we recognise this dependence of the manage- 

 ment of the laryngeal muscles on auditory sensations when we 

 talk of such or such one, who is deficient in this respect, as 

 "having no ear." 



913. The ventricles of the larynx appear to be useful in 

 allowing the vocal cords sufficient room for their vibrations ; they 

 also supply a secretion by which the vocal cords are kept ade- 

 quately moist. The purpose of the ventricular bands is not exactly 

 known ; it has been suggested that they may at times exert a 

 damping action by being brought down to touch the vocal cords ; 

 but this is very doubtful. The epiglottis, the position of which 

 as we have seen varies in different kinds of voice, has also an 

 influence on the character of the voice ; and further influences 

 which we shall consider under ' speech ' are exerted by the form of 

 the pharynx and the mouth. 



914. At the age of puberty a rapid development of the 

 larynx takes place, leading to a change in the range of the voice. 

 The peculiar harshness of the voice when it is thus ' breaking ' 

 seems to be due to a temporary congested and swollen condition 

 of the mucous membrane of the vocal cords accompanying the 

 active growth of the whole larynx. The change in the mucous 

 membrane may come on quite suddenly, the voice ' breaking ' for 

 instance in the course of a night. 



