344 



RESPIRATION 



[CH. XXIV. 



point opposite the third dorsal vertebra, where it divides into the 

 two bronchi, one for each lung (fig. 317). It measures, on an average, 



FIG. 317. Outline showing the general form 

 of the larynx, trachea, and bronchi, as 

 seen from the front, h, The great cornu of 

 the hyoid bone : e, epiglottis ; t, superior, 

 and t', inferior cornu of the thyroid carti- 

 lage ; c, middle of the cricoid cartilage ; 

 tr, the trachea, showing sixteen cartila- 

 ginous rings ; b, the right, and b', the left 

 bronchus. (Allen Thomson.) 



FIG. 318. Outline showing the general form of the 

 larynx, trachea, and bronchi, as seen from 

 behind, h, Great cornu of the hyoid bone ; 

 t, superior, and t', the inferior cornu of the 

 thyroid cartilage ; e, epiglottis ; a, points to the 

 back of both the arytenoid cartilages, which are 

 surmounted by the cornicula ; c, the middle 

 ridge on the back of the cricoid cartilage ; tr, the 

 posterior membranous part of the trachea ; 

 b, b', right and left bronchi. (Allen Thomson.) 



four or four and a half inches in length and from three-quarters of 

 an inch to an inch in diameter, and is essentially a tube of fibre-elastic 

 membrane, within the layers of which are imbedded a series of carti- 

 laginous rings, from sixteen to twenty in number. These rings ex- 



