THE ORGANS OF VOICE AND RESPIRATION. 



THE respiratory organs (apparatus respiratorius) consist of the larynx, or organ of 

 voice, the trachea, bronchi, lungs, and pleurae. 



THE LARYNX. 



The larynx, or organ of voice, is placed at the upper part of the air passage. 

 It is situated between the trachea and base of the tongue, at the upper and fore 

 part of the neck, where it forms a considerable projection in the middle line. 

 On either side of it lie the great vessels of the neck; behind, it forms part of the 

 boundary of the pharynx, and is covered by the mucous membrane lining that 

 cavity. Its vertical extent corresponds to the fourth, fifth, and sixth cervical ver- 

 tebrae, but it is placed somewhat higher in the female and also during childhood. 

 In infants between six and twelve months of age Symington found that the tip of 

 the epiglottis was a little above the level of the cartilage between the odontoid 

 process and body of the axis, and that between infancy and adult life the larynx 

 descends for a distance equal to two vertebral bodies and two intervertebral disks. 



According to Sappey, the average measurements of the adult larynx are as 

 follows : 



In males. In females. 



Vertical diameter 44 mm. 36 mm. 



Transverse diameter ........ 43 " 41 " 



Antero-posterior diameter 36 " 26 " 



Circumference 136 " 112 " 



Until puberty there is no marked difference between the larynx of the male and that of the 

 female. In the latter its further increase in size is only slight, whereas in the former the increase 

 is great; all the cartilages are enlarged, and the thyroid becomes prominent as the pomum Adami 

 in the middle line of the neck, while the length of the glottis is nearly doubled. 



The larynx is broad above, where it presents the form of a triangular box, 

 flattened behind and at the sides, and bounded in front by a prominent vertical 

 ridge. Below, it is narrow and cylindrical. It is composed of cartilages, which 

 are connected by ligaments and moved by numerous muscles. It is lined by 

 mucous membrane, which is continuous above with that lining the pharynx and 

 below with that of the trachea. On each side internal to the thyroid cartilage 

 a small recess, the recessus pyriformis, extends forward from the cavity of the 

 pharynx (p. 950). 



The Cartilages of the Larynx (cartilagines laryngis} are nine in number, three 

 single and three pairs: 



Thyroid. Two Arytenoid. 



Cricoid. Two Cornicula Laryngis. 



Epiglottis. Two Cuneiform. 



The Thyroid Cartilage (cartilage thyroidea) (Figs. 881 and 882) is the largest 

 cartilage of the larynx. It consists of two lateral lamellae or alae, united at an acute 



(1165) 



