910 THE ORdAXS OF VOICE 



broad, flat band which intL-rvfiU's Ijctwe'cn the vuntrifle of the larynx and the 

 inner surface of the thyroid cartihitre. 



The arytenoideus consists of transverse fibres passing from one arytenoid 

 cartilage to the other, and attached to their posterior concave surfaces. Super- 

 ficially are some oblicpie fibres, which decussate where they meet. These i)ass 

 from the outer angle of one cartilage l)elow to the summit of the opposite. A few 

 of these fibres pass onwards to the aryteno-epiglottidean fold and side of epiglottis. 

 These, reinforced liy fil)res attached Xo the sunnnit of the arytenoid cartilage, 

 constitute the aryteno-epiglottideus muscle. A few fibres l)lend with the thyro- 

 arytenoid nuiscle. 



' The arytenoideus approximates and depresses the arytenoid cartilages. These 

 actions are assisted by the aryteno-epiglottidei, which depress the epiglottis and 

 contract the superior aperture of the larynx. 



The thyro-epiglottideus (sometimes described as part of the thyro-arytenoid) 

 consists of fibres attaclu'(l below to the thyroid cartilage which, spreading al)ove. 

 reach the aryteno-epiglottidean fold, and the outer Avail of the laryngeal pouch as 

 well as the ei)iglottis. (For the nerve-supply of the laryngeal muscles see ]^age 912. ) 



The Interior of the Larynx. — The superior aperture, or opening of the 

 glottis, is triangular in shape, wide in front, narrow l)ehind, and placed so 

 obliquely as to be almost vertical in the living subject. Above and in front it is 

 bounded by the epiglottis, behind and below by the interarytenoid notch, whilst 

 on each side stretches the aryteno-epiglottidean fold containing muscular and liga- 

 mentous fil^res. This fold presents two thickened areas, one at the summit of the 

 arvtenoid cartilage, and one just in front and above this, formed by the bulging of 

 the cornicular and cuneiform cartilages respectively. 



Bounded internally by this fold, and externally l)v the wing of the thyroid 

 cartilage, is a shallow depression — the sinus pyriformis. 



The cavity of the larynx extends from the ajierture above described to the lower 

 border of the cricoid cartilage. 



Its lining of mucous membrane varies much in its colour and thickness and 

 its fixity to the structures which it overlies. On the surface of the true vocal cords 

 it is extremely thin, pale and adherent, whilst above and below this it is more 

 vascular and more loosely attached to the underlying parts. The submucous tissue 

 contains numerous elastic fibres and mucous glands. 



The cavity is naturally divided into two portions — supra- and infra-rimal — 

 divided l)y the glottis or interval between the two true vocal cords. 



The suprarimal portion corresponds to the space between the wings of the 

 thyroid cartilage. It is broad and triangular above, but narrower below, and its 

 walls are much deeper in front than l^ehind. Immediateh' above each vocal cord 

 is an oblong depression — the ventricle — bounded above by the crescent-shaped 

 edge of the false vocal cord, below b}' the straight margin of the true vocal cord, 

 and externally by the thyro-arytenoid muscle. The ventricle extends nearly the 

 whole length of the vocal cords, and is lined by a thin and tightly adherent mucous 

 membrane. It allows the free vibration of the true vocal cords in the production 

 of sound. From the anterior part of the ventricle there extends upwards, for about 

 half an inch, a small blind sac, named the laryngeal pouch. This reaches as high 

 as the up])er l)order of the thyroid cartilage; its mouth below is narrow and guarded 

 by two little folds of mucous membrane. A delicate fibrous investment is continued 

 from the true vocal cord around the sac. Some fatty tissue is enclosed within this, 

 and its mucous lining contains numerous glands. On its outer side are some 

 fibres of the thyro-arytenoid muscle; whilst on its inner side is a thiij layer of 

 muscular fibres, derived from the aryteno-e])iglotti(leus. and sometimes known as 

 Hilton's muscle, or the compressor sacculi laryngis. 



The superior or false vocal cords stand farther ai)art than the true, andcannoi 

 be made absohitely tense. Tliey liave already been sufficiently described. A 

 shallow fossa — the fossa innominata — is ol)servable, especially during ])honation, 

 between the false cord midtlie aryteno-e]>igl()ttidean fold; it is ]ilaced a little behind 

 the epiglottic. 



The inferior or true vocal cords are the structures concerned in the production of 

 the voice. They stretch from the vocal processes of the arytenoid cartUages to the 



