VOICE AND SPEECH 



433 



for it is in two separate bands unites the anterior process of 

 the arytenoid with the back surface of the thyroid just on the 

 outer side of the attachment into that cartilage of the vocal 

 cord. The internal thyro-arytenoid muscle is a comparatively 

 narrow band ; the external thyro-arytenoid muscle is thick 

 and broad.* By the simultaneous contraction of the encircling 



c 



D E 



Fia. 45. THE APERTURE OP THE GLOTTIS SEEN FROM ABOVE. 



The leaf-like structure in front of it is the epiglottis ; the two triangular structures at the back, 

 the arytenoid cartilages ; the white bands on either side, the vocal cords. A, The glottis is 

 widely open during inspiration. Arrows show the lines of action of the muscles which 

 rotate, and approximate, the cartilages. Attached to their outer angles, and pulling these 

 angles forwards, the lateral crico-arytenoid muscles ; pulling them backwards and inwards, 

 the posterior crico-arytenoid muscles. Drawing the cartilages together, the arytenoid 

 muscles. B, The glottis during speaking in a deep chest-voice, or when a low note of the 

 lower register is being sung. C, During the production of a high note of the lower register. 

 D, During the production of a note of the head-register. E, During the act of swallowing ; 

 the arytenoid cartilages are drawn towards the epiglottis ; the aperture is folded into a T ; 

 the pharynx (the tube behind the glottis) is distended. 



muscles the larynx is closely squeezed together, the anterior 

 portion of the slit forming a T, with the transverse limb in 

 front. This occurs only in swallowing. Under the co-operat- 

 ing contractions of the several muscles, the glottis assumes a 

 variety of shapes. The external crico-arytenoids rotate the 

 anterior angles of the arytenoid cartilages inwards (Fig. 45, A). 



* A bullock's larynx is an admirable object of study. In almost all points 

 of form and structure it is practically identical with the human larynx, and 

 its large size makes it easy to dissect, 



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