GLOTTIS AND LARYNGEAL POUCH. 155 



side ; and bounding the ventricle above and below are the whitish bands 

 of the vocal cords. 



If a probe be passed into that hollow, it will enter a small pouch (sac- 

 culus laryngis) by an aperture in the anterior and upper part. The dis- 

 sector should fill the sacculus on the left side by introducing a small piece 

 of cotton wool into it. 



The laryngeal space reaches from the epiglottis to the lower border of 

 the cricoid cartilage. It opens above into the pharynx, and below into 

 the trachea ; and in the intermediate portion are lodged the parts pro- 

 ducing voice. 



The tipper orifice of the larynx (fig. 29, N ) will be evident on placing 

 in contact the cut surfaces. It is triangular in shape, with the base in front 

 and the apex behind, and its sides are sloped obliquely downwards in the 

 antero-posterior direction. Its boundaries are, the epiglottis in front, 

 the arytienoid muscle and cartilages behind, and the arytieno-epiglottidean 

 fold of mucous membrane on each side. This aperture is closed by the 

 epiglottis during deglutition. 



The lower opening, limited by the inferior edge of the cricoid cartilage, 

 is circular in form, and is of the same size as that cartilage. 



The laryngeal cavity is much reduced in size within the thyroid car- 

 tilage by the vocal cords, and is dilated above and below them for the pur- 

 pose of allowing their free vibration. The lower dilatation may be seen 

 to be as large as the ring of the cricoid ; and the upper, much smaller, 

 corresponds with the ventricle of the larynx. Above the upper bulge the 

 wall of the larynx slants up to the epiglottis. 



The glottis or rima glottidis^ is the interval between the lower vocal 

 cords (fig. 44) ; it is placed on a level with the base of the arytrenoid car- 

 tilages, and is the narrowest part of the laryngeal cavity. 



Its sides are constructed partly of ligament and partly of cartilage : 

 thus, for about the two anterior thirds is the elastic vocal cord (fig. 42, B ), 

 whilst at the posterior third is the smooth inner surface of the arytaanoid 

 cartilage, E. Behind it is bounded by the aryta3noid muscle ; and in front 

 by the thyroid cartilage and the attachments of the vocal cords. 



The size of the interval differs in the two sexes. In the male it mea- 

 sures from before back nearly an inch (less a line), and across at the base, 

 when dilated, about a third of the other measurement. In the female the 

 dimensions will be less by two or three lines. 



Alterations in the size and form affect the interval where it is bounded 

 by the cartilages, as well as where it is limited by the ligaments. In the 

 former part, the changes are occasioned by the movements of the arytae- 

 noid cartilages ; but in the latter they are due to the lengthening and 

 shortening of the bands. 



In the state of rest it is a narrow fissure which is enlarged a little behind 

 and rounded ; but when dilated it is triangular in form, like the upper orifice, 

 though its wider part is turned backwards to the arytivnoid muscle. In the 

 living body the fissure is larger in inspiration than in expiration. The mus- 

 cles too are constantly producing alterations in the fissure, some acting more 

 immediately on the cartilages as dilators and contractors of the base; and 

 others altering the state of the ligaments, by elongating and shortening 

 the sides. 



The base is enlarged, and the interval rendered triangular by the poste- 

 rior crico-arytaenoid ; and is diminished by the arytienoid, and the lateral 

 crico-aryta?noid. And the ligamentous sides are elongated and made tense 

 by the crico-thyroidei, but are shortened by the thyro-arytojnoidei. 



