180 DISSECTION OF THE DOG 



orally by the ventricular fold and the base of the cuneiform cartilage. 

 The ventricular fold forms only a short ventral segment of the oral 

 boundary ; or, in other words, it forms a boundary to the entrance to the 

 appendix of the ventricle. It should be noted that the fold has, as a 

 basis, a fibrous band, the ventricular ligament (lig. ventriculare) , reaching 

 from the basal part of the cuneiform cartilage to the thyroid and epiglottis. 

 If the glosso-epiglottic fold of mucous membrane be removed, the under- 

 lymg hyo-epiglottic muscle will be revealed. At the same time the 

 hyoid attachment of the genio-glossal muscle will be made more clear than 

 ■was previously possible. 



M. HYO-EPiGLOTTicus. — The two hyo-epiglottic muscles arise independently 

 from the body of the hyoid bone, but blend as they proceed towards their 

 insertion, by a common tendon, into the middle line of the lingual surface of the 

 epiglottis. 



Dissection. — Clean up the nerves and vessels on the intact side of the 

 larynx. 



The nerves are the superior laryngeal and the recurrent. The former pierces 

 the hyo-thyroid ligament close to the oral thyroid cornu in company with the 

 superior laryngeal vessels. The recurrent nerve runs up the neck along the 

 dorsal border of the trachea. 



Dissection. — Strip the mucous membrane from the interior of the larynx, 

 and remove the remains of the muscles. Care must be exercised in the 

 removal of the membrane from the epiglottis, cuneiform and corniculate 

 cartilages, as these are fairly readily torn. The description of the various 

 cartilages, already given, should be again gone over. 



The connections of some of the cartilages have been described as the dis- 

 section proceeded, but there still remains to be discussed the attachment 

 of the epiglottis to the thyroid, the articulation betAveen the arytenoid 

 and cricoid cartilages, and the union of the two arytenoids. 



The petiolus of the epiglottis is attached to the thjrroid cartilage by the 

 thy ro- epiglottic ligament (lig. thyreo-epiglotticus), which, in conjunction with 

 the elasticity of the epiglottis itself, allows of free movement. 



Now that the restraining muscles have been removed, it is easy to demon- 

 strate that the movement between the thjrroid cornua and the cricoid cartilage 

 is mainly rotatory about a transverse axis running between the two joints. 



The crico-arytenoid joint is also diarthrodial, enclosed in the customary 

 joint-capsule. Movements are gliding in various directions, and rotatory 

 about a longitudinal axis. 



The two arytenoid cartilages are united by fibrous tissue, which is sufficiently 

 loose to allow of the necessary rotation in the crico-arytenoid joint. 



