THE LARYNX. 



343 



r-4- 



-8 



two ventricles ; in like manner the two auricles are sur- 

 rounded by a transverse plane of muscular fibres. Ulti- 

 mately the fibres are lost upon the cardiac septa and in the 

 coltimnae carneae, thence to be inserted by the chordae 

 tendinese upon the valves. The muscular fibre of the heart 

 is not invested by sarcolemma and consists of striated, 

 branched, and nucleated fibres. 



THE LARYNX. 



The larynx is placed in the 

 median line on the upper part 

 of the trachea. It is a pyra- 

 midal box composed of cartilages, 

 fibrous tissue, and muscles. The 

 cartilages are nine in number: 

 three single, thyroid, cricoid, 

 and epiglottis ; and three pairs, 

 arytenoid, cuneiform, and cor- 

 nicula laryngis. 



The thyroid consists of two 

 quadrilateral plates of cartilage 

 united in front at an acute angle. 

 Each plate is smooth and the 

 posterior border terminates in the 

 superior and inferior cornua. 

 The angle of junction forms a 

 projection at the anterior part of the neck called the 

 pomum Adami, or Adam's apple. 



The cricoid is a ring of cartilage shaped like a seal- 

 ring, the narrow part in front. Posteriorly it presents 

 two superior facets for the arytenoid cartilages, and 

 laterally a facet for articulation with the thyroid. 



The epiglottis is a leaflet of yellow-fibre cartilage 

 which is attached to the receding angle between the two 

 plates of the thyroid. Its normal position is vertical, but 



FIG. 148. VERTICAL SECTION 

 OF LARYNX. 



1 . body of hyoid bone ; 2, epiglot- 

 tis ; 3, thyro-hyoid membrane ; 4, great 

 cornu of hyoid; 5, false vocal cord: 6, 

 thyro-hyoid ligament: 7, ventricle of 

 larynx ; 8. thyro-hyoid membrane ; 9. 

 true vocal cord : 10, aryteno-epiglot- 

 tidean fold ; 11, thyroid cartilage ; 12, 

 superior cornn of thyroid ; 14, aryte- 

 noides muscle ; 16, arytenoid cartilage ; 

 18, coracoid cartilage. 



