THE NECK. 175 



superior margin of tlie smaller portion of the cartilage. 

 The whole interior margin affords attachment to the crico- 

 trachealis ligament, the anterior part of the superior 

 margin to the crico-thyroid ligament. The lateral parts of 

 the external surface to the crico-thyroid muscles. The 

 internal surface is lined by mucous membrane. 



The arytenoid cartilages, two in number, articulate 

 inferiorly by synovial joints with the cricoid cartilage. The 

 articulatory part is shaped like a prism, the inner angle of 

 which is elongated in a posterior direction towards its 

 fellow; the outer angle in an anterior direction towards 

 the epiglottis, with which it is indirectly connected by the 

 above-mentioned cartilaginous nodules. The superior ex- 

 tremity of the prismatic portion is expanded, and sends a 

 peculiar thin process in an anterior direction to be united 

 by mucous membrane to the epiglottis. Thus the external 

 surface presents two triangular spaces, into the posterior of 

 which arytenoideus is attached (running from one cartilage 

 to the other), into the anterior the thyro-arytenoidei j^os- 

 ticus and anticus, while crico-arytenoidei lateralis and pos- 

 ticus are attached to the prominent ridge between the two. 

 The superior margins of the arytenoid cartilages are con- 

 nected by continuity of their investing mucous membrane. 



From the internal surface of the arytenoid cartilages to 

 the inner surface of the thyroid cartilage and of the crico- 

 thyroid ligament run bands of yellow elastic tissue termed 

 the vocal cords, by the tension of which the sound of the 

 voice is modulated. They are covered on their internal 

 surface by the laryngeal mucous membrane, and externally 

 are in contact with the thyro-arytenoidei muscles ; the tri- 

 angular space between them is the rima glottidis. In our 

 description of the cartilages we have incidentally noticed 

 the different layers of yellow elastic tissue which, while 

 they serve to connect the different portions of cartilage 

 together, also by their elasticity cause them to return to 

 their normal position after allowing them to accommodate 

 themselves to the movements of the neighbouring parts. 

 The crico-thyroid, crico-trachealis, crico- arytenoid, and 

 thyro-hyoid ligaments therefore require no further descrip- 

 tion. The mucous membrane of the postero-inferior part 

 of the pharynx, after being reflected over the margin of the 

 arytenoid and epiglottic cartilages before investing the 

 vocal cords on either side, presents a diverticulum, the 



