DISSECTION OF THE LABYNX. 



231 



by the pitcher-like lip of the arytenoid cartilages and the fold of mucous 

 membrane uniting them, and laterally by the aryteno-epiglottic fold of 

 mucous membrane. During degluti- 

 tion the epiglottis is folded over the 

 aperture, which it closes like a lid. 



The Lower Aperture is circum- 

 scribed by the inferior edge of tlie 

 cricoid cartilage, and is directly con- 

 tinued by the lumen of tlie trachea. 



The Glottis, or Rima Glottidis. 

 This is a third aperture, placed about 

 the middle of the tube of the larynx, 

 which it divides into an upper and a 

 lower compartment. In its anterior 

 two-tliirds this opening lies between 

 the light and left vocal cords, and 

 in its posterior third it lies between 

 the bases of the arytenoid cartilages. 

 The size of the aperture is varied by 

 the movements executed in the crico- 

 arytenoid joints, as ah-eady seen ; and 

 its form varies with its size. It can 

 be completely closed by the apposition 

 of its margins in the mesial plane. Pic, 29. 



When it is only slightly opened, it is i,.,er.or of the Larvnx, seen from behind 



a slit-like anterO-pOSterior aperture^ i. Epiglottis ; 2. Arytenoia cartilage ; 21. 

 •i,,.i . 1 ]„j.„l Its base where it bounds the glottis; 3. Cut 



Widest at the centre ; when nK)derately ^.^rtace of cricoid cartilage ; 1 Vocai cord; 

 open, as in easy respiration, it has the ^i Jr*"''" °^ *^' larynx; o. Sub-epigiottic 

 form of an elongated isosceles triangle 



with the base behind ; when dilated to the fullest extent, it is lozenge- 

 shaped. 



The Ventricles, or Sinuses, of the larynx. Each of these is a recess, 

 or cavity, placed on the side of the larynx. The entrance to it lies above 

 the vocal cord, whose free straight edge, covered by mucous membrane, 

 forms the lower margin. The upper margin is formed by a concave fold 

 of mucous membrane, containing in man a few fibres designated the 

 false vocal cord. The cavity of the ventricle descends to the outer side 

 of the true vocal cord, and a pouch of the mucous lining of the cavity 

 passes out between the upper and lower divisions of the thyro-arytenoid 

 muscle. 



The Sub-epiglottic Sinus is a depression beneath the base of the 

 epiglottis, and provided with a lunated fold of mucous membrane. 



The Sub- arytenoid Sinus is a depression beneath the crico-arytenoid 

 joints. 



