



LARYNX. 69 



terior surfaces of the two aiytenoid cartilages ; the fibres of 

 this muscle consist of fasciculi, having partly a horizontal 

 or transverse, and partly an oblique direction. 



To expose the remaining muscles of the larynx, one side of the 

 thyroid cartilage must be removed. 



The CRICO-ARYTENOIDEUS LATERALIS MUSCLE arises from 



e lateral part of the upper border of the cricoid cartilage, 

 and is inserted into the muscular process of the arytenoid 

 cartilage. 



The THYRO-ARYTENOIDEUS MUSCLE arises from the angle 

 of the thyroid cartilage and is a complex muscle, imper- 

 fectly demonstrable in an ordinary dissection. One por- 

 tion, quadrangular in shape, passes backward to be inserted 

 into the vocal process of the arytenoid cartilage, and forms 

 the lower surface of the vocal cord. A second portion also 

 runs backward and is inserted into the lower part of the 

 antero-external surface of the aiytenoid cartilage, helping 

 to form the lower wall of the ventricle of the larynx. A 

 third portion sends its fibres in different directions ; some 

 pass backward to the lower part of the outer edge of the 

 arytenoid cartilage ; others passing along the outer wall of 

 the ventricle of the larynx lose themselves in the ary-epi- 

 glottidean fold ; others again pass partly into the ventricu- 

 lar cord and partly up to the epiglottis. 



The cavity of the larynx is divided into two parts by a 

 constriction caused by the prominence of two elastic fibrous 

 ligaments, attached in front to the angle of the thyroid car- 

 tilage, and posteriorly to the bases of the arytenoid car- 

 tilages. These are called the vocal cords, and the space 

 between them is called the rima glottidis. Immediately 

 above and running parallel with the vocal cords are two 

 folds of mucous membrane called the false cords, or, more 

 properly, the ventricular cords or bands. The space be- 

 tween the vocal cords and the ventricular bands is called 

 the ventricle of the larynx. 



In the ventricle of the larynx the mucous membrane 

 forms a deep pouch, best demonstrated by stuffing it with 

 cotton-wool ; this is called the sacculus laryngis, and is 

 directed upward, sometimes as high as the upper border of 

 the thyroid cartilage. 



The lateral boundaries of the upper laryngeal aperture 

 are formed by folds of mucous membrane, called the ary- 

 epiglottidean folds, which pass from the sides of the epi- 



