THE LARYNX 421 



Dissection. Remove the remains of the ary-epiglottic fold, the ventricular 

 and the vocal folds, and the lateral part of the conus elasticus on the 

 right side 6f the larynx, but be careful not to injure the arytrenoid cartilage 

 or the corniculate cartilage. Should the cuneiform cartilage be present 

 in the ary-epiglottic fold it should be detached and preserved. By this 

 dissection a closer view of the side wall of the laryngeal cavity can be ob- 

 tained. The undissected vocal fold of the left side should be examined 

 again, the laryngeal ventricle and appendix explored, and their precise 

 connections and extent determined. When the dissector has satisfied 

 himself upon these points he can proceed to display the vessels and nerves 

 of the larynx. The superior laryngeal artery and the internal laryngeal 

 nerve reach the pharynx by piercing the lateral thin part of the thyreo-hyoid 

 membrane, and they descend along the lateral wall of the recessus piriformis 

 to the larynx. By applying traction to the nerve, and at the same 

 time dividing the mucous membrane upon the medial surface of the thyreo- 

 hyoid membrane, they can easily be discovered. In following the branches 

 into which they divide, the mucous membrane must be gradually removed 

 from the wall of the larynx. The inferior laryngeal artery and nerve enter 

 from below and proceed upwards, under cover of the lamina of the 

 thyreoid cartilage. They can be satisfactorily displayed only by the 

 removal of this piece of cartilage, but the dissector is not recommended 

 to adopt this method unless another larynx is available for the examination 

 of the cartilages and joints. By drawing the thyreoid cartilage laterally 

 the more important branches can be studied. 



Ramus Internus of the Nervus Laryngeus Superior. 



In the dissection of the neck the internal laryngeal nerve was 

 seen springing from the superior laryngeal branch of the 

 vagus. It is a sensory nerve, and its branches are distributed 

 chiefly to the mucous membrane of the larynx. After pierc- 

 ing the lateral part of the thyreo-hyoid membrane, it divides 

 into three branches. The uppermost of these sends filaments 

 to the ary-epiglottic fold, to the mucous membrane which 

 covers the epiglottis, and to the three folds anterior to it. 

 The twigs which go to the epiglottis ramify on its posterior 

 surface, but many of them pierce the cartilage to reach the 

 mucous membrane on its anterior surface. The intermediate 

 branch of the internal laryngeal nerve breaks up into filaments, 

 which are given to the mucous membrane lining the side wall 

 of the larynx. The lowest branch descends and gives filaments 

 to the mucous membrane which covers the lateral and 

 posterior aspects of the arytaenoid and cricoid cartilages. A 

 fairly large twig, which proceeds from this branch, runs down- 

 wards upon the posterior aspect of the cricoid cartilage to join 

 the laryngeal branch of the recurrent nerve. 



Nervus Recurrens. The recurrent nerve has previously 

 been seen arising from the vagus, and it has been traced, in 

 the neck, up to the point where it disappears under cover of 



ii 27 a 



