THE HEAD AND NECK 



1285 



and it has a characteristic peariy white colour. The true \'ocal 

 cords are much nearer to each other than the false, so that the 

 latter are not visible when the larynx is viewed from below. 



Rima Glottidis. — ^The rima glottidis, or glottis vera, is the narrow 

 fissure by which the upper and lower compartments of the larynx 

 communicate with each other, and it is the narrowest part of the 

 cavity. It is elongated from before backwards, and is narrow 

 in front at the receding angle of the thyroid cartilage, but wider 

 behind, where it is closed by the interarytenoid fold of mucous 

 membrane. It is divisible into an interchordal portion, called the 

 glottis vocalis, and an interarytenoid portion, called the glottis 

 respiratoria. The glottis vocalis is narrow, and is bounded on either 

 side by the true vocal cord. Its length, as stated, is rather less 

 than an inch, and it forms about two-thirds of the entire glottis. 



Thyroid Notch 



Ala of Thyroid Cartilage 



Thyro-arytaenoideus 

 True Vocal Cord 



Crico-arytaenoideus Lateralis 

 Arytenoid Cartilage 



Fig. 



Crico-arytaenoideus Posticus 



Arytaenoideus 



533. — Dissection of the Larynx, showing the Muscles, True 

 Vocal Cords, and Rima Glottidis (Superior View). 



The glottis respiratoria is wider than the glottis vocalis, and is 

 bounded on either side by the inner aspect of the base of the 

 arytenoid cartilage. It is about ^ inch in length, and forms about 

 one-third of the length of the entire glottis. 



The shape of the rima glottidis is subject to alteration, and has 

 to be considered under three conditions. 



(i) During quiet respiration it has the form of an elongated 

 triangle, the apex being in front at the thyroid cartilage, and the 

 base behind at the interarytenoid fold of mucous membrane. 



(2) During a deep inspiration the rima is widely dilated, and assumes 

 a somewhat diamond-shape, the widest part being opposite the tips 

 of the vocal processes of the arytenoid cartilages, where the lateral 

 angles of the diamond are placed, the posterior angle, at the 

 interarytenoid fold of mucous membrane, being truncated. 



(3) During vocalization, phonation, and especicdly in singing high 



