THE LARYNX 403 



less than 1 inch long, and according to its degree of dilatation, 

 from ^ to ^ inch wide. In easy respiration its form is triangular, 

 with the base posterior, and when fully dilated it is lozenge- 

 shaped. 



The superior or false vocal cords are two mucous folds, each 

 enclosing the corresponding superior thyroarytenoid ligament. 

 This latter is a thin band running between the angle of the 

 thyroid and the anteroexternal surface of the arytenoid cartilage. 



The inferior or true vocal cords are two strong bands, the 

 inferior thyroarytenoid ligaments, covered by mucous mem- 

 brane and attached to the depression between the alae of the 

 thyroid cartilage in front and the anterior angle of the base 

 (vocal process) of the arytenoid cartilages behind. Below, 

 each is continuous with the lateral part of the crico thyroid 

 ligament or membrane. Part of the thyroarytenoidei is external 

 and parallel to them. 



The ventricles of the larynx lie one on each side, between the 

 upper and lower vocal cords, bounded externally by the thyro- 

 arytenoidei. At the front a narrow opening leads into a blind 

 pouch, the laryngeal saccule. 



The saccule of the larynx is a space on each side, between the 

 false vocal cord and the inner surface of the thyroid cartilage, 

 reaching upward as high as the upper border of that cartilage, 

 and its mucous membrane presents the orifices of sixty or 

 seventy glands. This space has a fibrous capsule. Its laryngeal 

 surface is covered by the inferior arytenoepiglottic muscle, 

 or compressor sacculi laryngis, and its external surface by the 

 thyroarytenoideus and thyroepiglottic muscles. 



The muscles of the larynx are divided into extrinsic and 

 intrinsic the former will be found under the muscle system 

 (p. 159). The latter are: 



The cricothyroid arises from the front part and sides of the 

 cricoid cartilage, and is inserted into the lower border of the 

 thyroid cartilage and the front of its lower cornu. Separating 

 the inner borders of these two muscles is the central part of 

 the cricothyroid membrane. The action of the two muscles 

 is to approximate the cricoid to the thyroid and thus tense the 

 vocal cords. The nerve supply is from the superior laryngeal. 



The thyroarytenoid is divided into two parts, outer and inner. 

 It arises in front from the angle of the thyroid at its lower 

 part, and its inner part is inserted into the vocal process and 



