1106 



THE ORGANS OF VOICE AND RESPIRATION. 



cess of the base of the arytenoid cartilage. The upper fibres are nearly horizontal, 

 the middle oblique, and the lower almost vertical. 1 



The Crico-arytenoideus lateralis is smaller than the preceding, and of an 

 oblong form. It arises from the upper border of the side of the cricoid cartilage, 

 and, passing obliquely upward and backward, is inserted into the muscular process 

 of the base of the arytenoid cartilage in front of the preceding muscle. 



The Arytenoideus is a single muscle filling up the posterior concave surface 

 of the arytenoid cartilages. It arises from the posterior surface and outer border 



of one arytenoid cartilage, and is in- 

 serted into the corresponding parts of 

 the opposite cartilage. It consists of 

 three planes of fibres, two oblique and 

 one transverse. The oblique fibres, 

 the most superficial, form two fasciculi, 



Cornicida 

 laryngis. 



Articular facet for 

 inferior cornu of 

 thyroid cartilage. 



FIG. 70S. Muscles of larynx, 

 of thyroid cartilage removed. 



Side view. Right ala 



FIG. 704. Interior of the larynx, seen 

 above. (Enlarged.) 



from 



which pass from the base of one cartilage to the apex of the opposite one. The 

 transverse fibres, the deepest and most numerous, pass transversely across between 

 the two cartilages ; hence the Arytenoideus was formerly considered as several mus- 

 cles, under the name of transversi and obliqui. A few of the oblique fibres are 

 usually continued round the outer margin of the cartilage, and blend with the 

 Thyro-arytenoid or the Aryteno-epiglottideus superior muscle. 2 



The Thyro-arytenoideus is a broad, flat muscle, which lies parallel with the outer 

 side of the true vocal cord. It arises in front from the lower half of the receding 

 angle of the thyroid cartilage and from the crico-thyroid membrane. Its fibres 

 pass backward and outward, to be inserted into the arytenoid cartilage. This 

 muscle consists of two fasciculi. The inner portion, the thicker, is inserted into 

 the vocal process of the base of the arytenoid cartilage and into the adjacent por- 



1 Dr. Merkel of Leipsic has described a muscular slip which occasionally extends between the 

 outer border of the posterior surface of the cricoid cartilage and the posterior margin of the inferior 

 cornu of the thyroid; this he calls the "Musculus kerato-cricoideus." It is not found in every 

 larynx, and when present exits usually only on one side, but is occasionally found on both sides. 

 Sir William Turner (Edinburgh Medictd Journal, Feb., 1860) states that it is found in about one case 

 in five. Its action is to fix the lower horn of the thyroid cartilage backward and downward, oppos- 

 ing in some measure the part of the Crico-thyroid muscle which is connected to the anterior margin 

 of the horn. 



2 The arytenoideus reclus (Luschka) is a small slip passing between the posterior surface of the 

 arytenoid cartilage below to the cartilage of Santorini (corniculum) above. Anatomy, Hyrtl, p. 718. 



