LAKYKX. 



LARYNX. 



35J 



The AryVnoid O 



the form of an irregular t rion- 



he upper edge of the 



\\ ' ' 



rae AryvnoKl uarusMe* nave eacn w IOTO 

 nkr pyramid <jty. 3). They re PS*** P< ** 



bcoed put <rf the crioold cartilage, iua* within the 



pert o/the angle farmed by the needing plate, of the thyroid. The 

 EMM () by which each i. articulated with the cricoi.l U slightly cop- 

 cav., perfectly smooth, and capable of moTing to a certain extent in 

 tnrr direction. 



The Epiglottis OTj. 4) U of a somewhat ovt form. It is attached 

 by t epex * *he angle of union of the plates of the thyroid cartilage, 

 and projects obliquely backwards and upwards over the cricoid and 

 arytnxnd cartilages bke a shield, guarding them from the contact of 

 foreign bodies passing from the mouth. 



These cartilages are connected chiefly by elastic ligament, which U 

 arranged in bands of varying thickness throughout the whole of the 

 larynx, uniting the upper edge of the thyroid cartilage to the 01 

 hyoide*, and its lower edge to the cricoid cartilage ; passing also from 

 the arytenoid cartilages to the epiglottis, and uniting the rings of the 

 trachea and bronchi ; affording to all a 6rm but yielding connection, 

 and endowing them by its elasticity with the power of resounding in 

 accordance with the ribrations originating in the vocal ligaments. 



The Vocal Ligament* are two narrow bands of highly-elastic tissue, 

 itrrtrhH between toe anterior angle of the thyroid and the anterior 

 surfaces of the the arytmoid cartilage*. The substance of which 

 they an composed is a yellowish dense fibrous tissue, which is placed 

 in those part* of the body where a permanent elasticity is required, 

 M in the spaces between the lamina; of the vertebra, the coats of 

 arterieii, the rings of the trachea, Ac. In fy. 5 a profile view of the 



Hg. 6. 



; ; : 



light vocal ligament i* drawn : a, a, a i* the outline of the thyroid 

 cartilage, of which part of the left side is removed ; 6 is the cricoid 

 cartilage, and c the arytenoid cartilage of the right side ; d, d is the 

 vocal ligament. In fig. the view of the vocal ligament* (a) is 

 taken so seen from above ; they are attached anteriorly to the inside 

 of th* thyroid cartilage at i, and posteriorly to the front of the ary- 

 Uaoid cartibwe* (t, t\ Between them is the aperture through which 

 we breathe, the glottis (</) ; it i* bounded posteriorly by the inner 



and the crioc-thyroid muscle will therefore produce a rotatory motion 

 of the cricoid cartilage around the horizontal axis drawn through /. 

 When the anterior edge of the cricoid cartilage U thus raised toward* 

 the anterior angle of the thyroid it* posterior and upper part will be 

 moved backwards and downwards to a greater distance from the front 

 of the thyroid ; and if the arytenoid cartilages be fixed on the top of 

 the cricoid, they will of course move with it in the same direction. 

 The distance between their anterior edges and the angle of the 

 thyroid (jly. 5) will thus be increased, and the vocal ligaments (</, d), 

 which are attached to tho*e points, will be proportionally stretched. 



The Thyro-Arytenoidei (fig. 0, t, e) are attached anteriorly by the 

 aides of the angle of the thyroid cartilage to the outer side of, and 

 above, the vocal ligaments, and posteriorly to the anterior angles and 

 outer edges of the arytenoid cartilages. Their simplest action will 

 therefore be to approximate the same points which the preceding 

 muscles render more remote ; they will thus shorten and relax the 

 vocal ligament*. Some of their fibres extend on each side for a short 

 distance above and below the vocal ligaments; those below have the 

 power of narrowing the access to the glottis, while those above the 

 ligaments may compress together the sides of the larynx directly over 

 the glottis. Lastly, there are other fibres which are attached to tho 

 outer edges of the vocal ligament* themselves. 



The Crico-Arytenoidei Postici (Jig. 9, 6, i) are attached to the posterior 

 surface of the cricoid cartilage (a, a), and pass obliquely outwards, to 

 be inserted into the outer angle of the arytenoid cartilages. In con- 

 tracting therefore, if the arytenoid cartilages be moveable, they will 

 draw their anterior angles outwards, and thus increase the width of 

 the glottis ; but if the arytenoid cartilages be fixed by other muscles, 

 the'crico-arytenoidei postici will merely draw them backwards and 

 stretch the vocal ligament*. 



speaking 

 narrow,d (fig. 11, the continued line*). 



on the parts of the larynx just described are 

 1 attached to corretponding points on each 

 iir name* are compounded of those of the 

 eartilsges on which they are inserted, as follows : 



Tbe Crieo-Thyrotdeus (fiy.S.a,a, and fig. 6, t) i* attached on each 

 aide, at one of its eitrrmiUe., to the 



Th Muscle* acting on th 

 ruined symmetrically and a 

 elderf UM larynx ; and their 

 Mtflajes en which they are h 



Tbe Crieo-Tbyroideu* (fig. I 



id*, at one of its extremities, to the upper edge of the narrow front 

 pert of the cricoid cartilage ; and at the other, to the lower edge of 

 the thyroid, ju.t before its lower horn. It* fibre* are directed 

 apwanU and backwards, and it* immediate action would therefore be 

 to approximate the adjacent edge* of the thyroid and cricoid cartilages. 

 Bat the thyroid is Axed on each aid* by a ligament paw-ins from its 

 inferior horn to the aide of the broad part of the cricoid (fy. 5,f), 



The Crico-Aij tenoidei Laterales (fig. 7, c) are attached on tho our. 

 hand to the inner sides of the cricoid cartilage (a), and on the other 

 to the outer angles of the orytenoids (6); they rotate the latt.r 

 inwards, so as to approximate their front portions and narrow the 

 anterior part of the glottis. 



The Posterior Arytenoid Muscles (fig. 9, c, c) lie behind the ary- 

 tenoid cartilages, and consist of fibres passing transversely and 

 obliquely from one to the other. They therefore simply approximate 

 these bodies, and narrow or close the back part of the glottis. 



The simplest actions of all these muscles in regard to the voice may 

 therefore be thus stated : the crico-thyroidei stretch the vocal liga- 

 ments; the tbyro-ary tenoidei relax them; the crico-ary tenoidei postici 

 open the glottis ; the crico-arytenoidei latencies and the arytenoidei 

 postici narrow or close it 



A band of muscular fibre* may be also mentioned as passing from 

 the aryteuoid cartilages to each tide of the epiglottis, and thus serving 

 to draw down the latter so that it may cover the glottis more closely 

 than when left to its own elasticity. 



Below, the larynx opens into tho trachea (fig. 10, 8), which M 

 continued into the chest, and there divides into two branches, the 

 bronchi, whose ramifications and terminations form the air-passage* 

 and air-cells of the lungs. The lungs, being exactly contained in tho 

 cavity of the chest, are compressed by the contractions of its wnllx. 

 The walls of the chest ore therefore the power by which the air is 

 forced from the lungs through tho glottis for the production of tho 

 voice, and it is by their more or leas powerful contraction that the 

 various degree* of intensity of the same note are produced. Tho 

 trachea U composed of a senes of cartilaginous incomplete rings which 

 are united behind by muscular fibres, and are connected together by 

 longitudinal clootie band*. It ii thus capable of variations both of 

 length, breadth, and tension ; and of entering into vibrations with 

 the column of air contained in it, and of assisting in communicating 

 those vibrations through it* branches to the walls of the chest. 



At tho upper part of the trachea the windpipe gradually narrows 

 towards the glottis (see view of it* section in fig. 12) ; and above tl.e 

 glottis it suddenly dilates, so that the edges of the elastic 

 ligament* stand out from tho wall of the larynx, and have space in 

 which they may vibrate freely, like tho lijm in the mouthpiece of a 

 trumpet. About half an inch higher the passage again contract*, HO 

 as to form a narrow recess on each side, directly above the vocal 

 cords. This is called the ventricle of the larynx, and the prominent 

 bands above it are called the false vocal cords, or the upper ligaments 



