336 Mr Wilms on the 



But upon singing a scale of notes two motions are to be ob- 

 served in these cartilages; one is a general motion upwards, when 

 the pitch of the notes rises, and downwards, when it falls ; which 

 we have no concern with at present, as we are treating only of 

 the motions of the laryngeal cartilages with respect to each other, 

 which this does not affect. The other motion consists of the relative 

 motion of the cricoid D and the point E of the thyroid, and con- 

 sequent variation in the distance DE, which is best to be traced 

 by lodging the tip of the finger in the little hollow between the 

 cartilages, and so following the general motion up and down. 

 By doing this carefully, the size of this aperture will be perceived 

 to follow a law exactly coinciding with the above explanation, 

 namely, always increasing with a descending pitch and diminishing 

 with a rising one.* 



So far, the arytenoids have merely served as links, connecting the 

 vocal ligaments and thyroarytenoid muscles with the cricoid cartilage, 

 and the function just described would be just as well performed if 

 the vocal ligaments and thyroarytenoid muscles were attached to the 

 cricoid at B without their intervention. In fact, were the vocal liga- 

 ments merely intended to sound whenever the current of air passed 

 through the larynx these cartilages would apparently have no office. 



But it is to be remembered, that to enable the -ligaments to 

 vibrate they must be made to assume a peculiar position with 

 respect to each other, and that for breathing, it is necessary that we 

 have the means of opening the passage wide, also of entirely closing 

 it ; during which it is essential that that peculiar position be avoided, 

 for fear of a sound being produced when not intended. It is in the 

 performance of all these motions that the arytenoids are concerned. 



* Vide Note D. 



