CAVITY OF THE LAKYNX. 1071 



more than half of its length, and called the pars intermembranacea of the rima 

 glottidis ; (2) a broader, , shorter portion, between the arytaenoid cartilages, and 

 termed the pars intercartilaginea. By changes in the position of the arytsenoid 

 cartilages the form of the rima glottidis undergoes constant alterations. In 

 ordinary easy breathing it is somewhat lanceolate in outline. The pars inter- 

 membranacea presents, under these conditions, the form of an elongated triangle 

 the base of which is directed dorsally and corresponds to an imaginary line drawn 

 between the points of the vocal processes of the arytaenoid cartilages, whilst the 

 pars intercartilaginea is somewhat quadrangular. When the glottis is opened 

 widely the broadest part of the fissure is at the extremities of the vocal processes 

 of the arytsenoids, and there each side of the rima glottidis presents a marked angle. 

 The two vocal folds, on the other hand, may be approximated to each other so 

 closely, as in singing a high note, that the pars intermembranacea is reduced to a 

 linear chink. 



The length of the rima glottidis differs very considerably in the two sexes, and upon this 

 depends the different character of the voice in the male and female. According to Moura, the 

 following are the average measurements in the quiescent condition of the rima : 



Male-Length of entire ri ,na glottidia, 23 nun. 



Female Length of entire rima glottidis, 17mm. / P ars intermembranacea, 11-5 mm. 



( pars intercartilaginea, 5*5 mm. 



By stretching the vocal folds, however, the length of the rima glottidis in the male may 

 be increased to 27'5 mm., and in the female to 20 mm. 



The position of the rima glottidis may be indicated on the surface by marking a point on the 

 middle line of the neck 8'5 mm. below the thyreoid notch in the male and 6*5 mm. in the 

 female. This is the average position (Taguchi). 



Ventriculus Laryngis (Morgagnii). The lateral wall of the larynx, in the 

 interval between the ventricular and the vocal folds, exhibits a marked pocket- 

 like depression or recess called the ventricle of the larynx. The ventricle passes 

 upwards, so as to undermine somewhat the ventricular fold, and its mouth is 

 somewhat narrower than its cavity. Ventrally it reaches to the angle between 

 the laminse of the thyreoid cartilage, whilst dorsally it ends at the ventral border 

 of the arytajnoid cartilage. 



Under cover of the ventral part of the ventricular fold a small slit-like 

 aperture may be detected ; this leads upwards from the laryngeal ventricle into a 

 small diverticulum of mucous membrane, termed the appendix ventriculi laryngis, 

 which passes upwards, between the ventricular fold and the lamina of the 

 thyreoid cartilage. The laryngeal appendix is of variable extent, but as a rule it 

 ends blindly at the level of the upper border of the thyreoid cartilage. 



Sometimes the appendix ventriculi laryngis extends much higher up, and may even 

 reach the dorsal part of the great cornu of the hyoid bone. This is of interest when 

 considered in connexion with the extensive laryngeal pouches of the anthropoid apes. 



The lowest compartment of the cavity of the larynx leads caudally into the 

 trachea. Above it is narrow and compressed laterally, but it gradually widens 

 out until it becomes circular, in correspondence with the trachea, with which 

 is continuous. It is bounded by the sloping medial surfaces of the conus 

 elasticus (O.T. crico - thyreoid membrane) and by the medial aspect of the 

 cricoid cartilage both covered with smooth mucous membrane. In the operation 

 of laryngotomy the opening is made through the crico-thyreoid ligament in the 

 ventral wall of this compartment. 



Tunica Mucosa Laryngis. The mucous membrane which lines the larynx 



continuous above with the lining of the pharynx, and below with the mucous 



tembrane of the trachea. Over the dorsal surface of the epiglottis it is closely 



Iherent, but elsewhere, above the level of the vocal folds, it is loosely attached 



ubmucous tissue which extends into the ary-epiglottic folds. As it passes over 



' vocal folds the mucous membrane is very thin, and is tightly bound down. 



t is important to bear these facts in mind, because, in certain inflammatory conditions, the 

 iubmucous tissue in the upper part of the larynx is liable to become infiltrated with fluid, 



