VOICE AND SPEECH. 



tcr of their results, have done much to simplify the study of 

 the muscular acts concerned in the production of the voice. 



Bearing in mind the relations and attachments of the 

 vocal chords, we can understand precisely how they can be 

 rendered tense or loose by muscular action. Their fixed 

 point is in front, where their extremities, attached to the 

 thyroid cartilage, are nearly or quite in contact with each 

 other. The arytenoid cartilages, to which they are attached 

 posteriorly, present a movable articulation with the cricoid 

 cartilage ; and the cricoid, narrow in front, and wide behind, 

 where the arytenoid cartilages are attached, presents a mov- 

 able articulation with the thyroid cartilage. It is evident, 

 therefore, that muscles acting upon the cricoid cartilage can 

 cause it to swing upon its two points of articulation with the 

 inferior cornua of the thyroid, raising the anterior portion 

 and approximating it to the lower edge of the thyroid ; and, 

 as a consequence, the posterior portion, which carries the 

 arytenoid cartilages and the posterior attachments of the 

 vocal chords, is depressed. This action would, of course, in- 

 crease the distance between the arytenoid cartilages and the 

 anterior portion of the thyroid, elongate the vocal chords, 

 and subject them to a certain degree of passive tension. 

 Experiments have shown that such an effect is produced 

 by the contraction of the cri co-thyroid muscles. 



The articulations of the different parts of the larynx 

 are such that the arytenoid cartilages may be approximated 

 to each other posteriorly, though perhaps only to a slight 

 extent, thus diminishing the interval between the posterior 

 attachments of the vocal chords. This action can be effected 

 by contraction of the single muscle of the larynx, the aryte- 

 noid, and also by the lateral crico-arytenoid muscles. The 

 thyro-arytenoid muscles, the most complicated of all the in- 

 trinsic muscles in their attachments and the direction of 

 their fibres, according to Longet, give rigidity and increased 

 capacity of vibration to the vocal chords. 1 



1 Op. tit., p. 730. 



