152 SURGICAL ATPLIKD ANATOMY. [Chnp. <x. 



child of three months it reaches the lower border of 

 the atlas, and at six years the lower border of the 

 axis (Symington). With the laryngoscope the follow- 

 ing parts may be made out : The base of the tongue 

 and glosso-epiglottic ligaments ; the superior aperture 

 of the larynx, presenting in front the epiglottis, at the 

 sides the aryteno-epiglottidean folds (in which are two 

 rounded eminences corresponding to the cornicula and 

 cuneiform cartilages), and at the back the arytenoid 

 commissure of mucous membrane. Deeply down can 

 be seen the true and false vocal cords, the ventricle, 

 the anterior wall of the larynx, a little of the cricoid 

 cartilage, and more or less of the anterior wall of the 

 trachea If the glottis be very fully dilated the open- 

 ings of the two bronchi may be dimly seen. 



The thyroid and cricoid cartilages, and the 

 greater part of the arytenoid, are in structure hyaline, 

 as are the costal cartilages. Like the last-named, they 

 are liable to become more or less ossified as life ad- 

 vances. Ossification commences in the thyroid and 

 cricoid cartilages at about the age of 20, and in either 

 cartilage the process commences in the vicinity of the 

 crico-thyroid joint. The arytenoid ossifies later. 

 Ossification of the laryngeal cartilages is more marked 

 in males than in females. The larger cartilages are 

 liable to be fractured by violence, as by blows, throt- 

 tling, etc. The thyroid is the one most frequently 

 broken, and usually in the median line. 



The riiiia glottidis is the aperture between the 

 true vocal cords in front and the bases of the arytenoid 

 cartilages behind. It is the narrowest part of the 

 interior of the larynx, and it is well to be familiar 

 with its proportions in reference to the entrance of 

 foreign bodies, and the introduction of instruments. 

 In the adult male the rima measures nearly one inch 

 (11 lines) from before backwards ; from side to side, 

 nt its widest part, it measures about one-third of the 



