450 '////: Hrsi'Ilt.lTOUY Al'J'AJi.lTI s l\ .V.1.V.V.I /./.I. 



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

 cumference of llio 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 bo followed by a notice of 

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

 receive attention. 



STRUCTURE OF THE LARYNX. It comprises in its structure : 1, A crti- 

 lii'ji nous framework, composed of five pieces; 2, Muscles which move these 

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

 4, Vessels and nerves. 



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

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

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



CRICOID CARTILAGE. This cartilage, as its name indicates (K/HKOS, ctSos, 

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

 on each side, but all the less as tho animal has its respiratory apparat us 

 well developed, this ring offers two faces, and two borders or circumfcr< //<'.. 

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

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

 a little eminence more or less prominent, elongated in tho 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 tho thyroid cartilage. 

 Nothing remarkable is to bo 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 tho narrow part opposite the bezel, 

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

 arytenoid cartilages. Tho inferior circumference responds to tho first ring 

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

 bezel. 



THYROID CARTILAGE (0vpeos, eTSos, 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 tho terminal 

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

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

 articulates. 



Tho plates, lateral branches, or aloe of tho thyroid present two faces, two 

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

 by the hyo-thyroidcus and thyro-pharyngeus muscles. The internal fur,-. 

 slightly concave, is covered, near the superior border, by tho 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-staphylcus (palato-pharyngcus) 

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

 obtuse angles of the parallelogram represented by each lateral plato of tho 

 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 tho superior 

 laryngcal nerve. The inferior border is also divided into two parts by tho 

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



