4 50 THE EESPIRA TORY APPARA TVS IN MAMMA LI A . 



pharynx, and by means of the walls of the latter is attached to the cir- 

 cumference of the posterior openings of the nasal cavities. 



In order to facilitate description, this brief notice of its form, situation, 

 general relations, and mode of attachment will be followed by a notice oi 

 its structure ; afterwards, the study of its external and internal surfaces will 

 receive attention. 



STRUCTURE OP THE LARYNX. It comprises in its structure : 1, A carti- 

 laginous framework, composed of five pieces; 2, Muscles which move these 

 pieces ; 3, A mucous membrane spread over the inner surface of the organ ; 

 4, Vessels and nerves. 



1. Cartilaginous framework of the larynx. In this we find : three single 

 median cartilages, the cricoid, thyroid, and epiglottis; and two lateral 

 cartilages, the arytenoid. All are movable one upon the other. 



CRICOID CARTILAGE. This cartilage, as its name indicates (K/SI'KOS, eTSos, 

 like a ring), is exactly like a ring with a bezel looking upwards. Depressed 

 on each side, but all the less as the animal has its respiratory apparatus 

 well developed, this ring offers two faces, and two borders or circumferences. 

 The internal face is smooth and covered by mucous membrane. The external 

 face is provided, in the middle of the widened portion forming the bezel with 

 a little eminence more or less prominent, elongated in the form of a crest, 

 and separating the two posterior crico-arytenoid muscles, to which it gives 

 attachment, from each other. On the sides of this bezel are two small, articular, 

 concave facets, which correspond to the branches of the thyroid cartilage. 

 Nothing remarkable is to be noted for the remainder of the extent of this face. 

 The superior circumference, comprised laterally between the two branches of 

 the thyroid cartilage, is hollowed out in the narrow part opposite the bezel, 

 where its shows two lateral convex articular facets for articulation with the 

 aryteuoid cartilages. The inferior circumference responds to the first ring 

 of the trachea ; it offers a small notch, often double, on the middle of the 

 bezel. 



THYROID CARTILAGE (Ovpcos, eISt>s, like a shield}. This is composed 

 of two lateral plates, which have the form of an obliquangular parallelo- 

 gram, and are united at their anterior extremity to form a thick constricted 

 part which, in Veterinary Anatomy, is named the "body of the thyroid. This 

 body is smooth on its inferior face, where it is covered by the terminal 

 extremity of the subscapulo-hyoideii muscles. On its superior face is 

 an obtuse, rounded, and irregular protuberance, on which tlfe epiglottis 

 articulates. 



The plates, lateral branches, or ales of the thyroid present two faces, two 

 borders, and two extremities. The external face, slightly convex, is covered 

 by the hyo-thyroideus and thyro-pharyngeus muscles. The internal face, 

 slightly concave, is covered, near the superior border, by the pharyngeal 

 mucous membrane ; for the remainder of its extent it responds to the thyro- 

 arytenoid and lateral crico-arytenoid muscles. 



The superior border is divided by a small prolongation into two parts : 

 an anterior, giving attachment to the thyro-hyoid membrane ; the other 

 posterior, into which is inserted the pharyngo-staphyleus (palato-pharyngeus) 

 muscle. This appendix, the great thyroid cornu of Man, forms one of the 

 obtuse angles of the parallelogram represented by each lateral plate of the 

 thyroid cartilage ; it is united to the extremity of the hyoid cornu ; and at 

 its base is an opening, or deep notch, through which passes the superior 

 laryngeal nerve. The inferior border is also divided into two parts by the 

 second obtuse angle of the cartilage : the anterior part forms, with that of 



