HEAD AND NECK OF THE HORSE 93 



into the oblique line on the lateral surface of the lamina of the thyroid 

 cartilage. 



M. HYOIDEUS TRANSVERSUS. — The transverse hyoid muscle is small 

 and. single, pale in colour, and runs across from one lesser cornu of the 

 hyoid bone to the other on the opposite side of the head. 



The larynx. — The larynx^ is a tubular organ situated immedi- 

 ately behind the root of the tongue and ventral to the pharynx and the 

 beginning of the eesophagus. Laterally and dorsally it is related to the 

 constrictor muscles of the pharynx, v^^hile laterally and ventrally it is 

 covered by the thyro-hyoid, sterno-thyroid and sterno-hyoid muscles. 

 Its function is to produce voice, guard against the entrance of foreign 

 bodies into the trachea, and regulate the amount of air respired. The 

 organ is provided with a skeleton of cartilages, upon which muscles act 

 in such a way as to cause variation in the character of the interior of 

 the tube. The interior itself is lined by mucous membrane continuous, 

 on the one hand, with that of the pharynx, and, on the other, with the 

 lining of the trachea. 



Seeing that it is well nigh impossible to obtain an intelligent grasp 

 of the arrangement of the muscles, &c., without knowing something of 

 the parts with which they are connected, an account of the laryngeal 

 cartilages is given here instead of later ; and it will be well that the 

 dissector procure a set of disarticulated cartilages in order that he may 

 familiarise himself with their form and parts before beginning the 

 actual dissection of the larynx. 



The cartilages of the larynx (Cartilagines laryngis). — The 

 larynx contains nine cartilages, of which three are single — thyroid, 

 cricoid and epiglottis — and the rest are in pairs — arytenoid, cornicu- 

 late and cuneiform. In the horse the corniculate cartilages are fused 

 with the arytenoids, and the cuneiform with the epiglottis. 



The thyroid cartilage (cartilago thyreoidea) is the largest, and con- 

 sists of two quadrilateral lamince - meeting and fused in the mid- 

 ventral line at a narrow isthmus, that forms a slightly projecting 

 laryngeal prominence (prominentia laryngis). The dorsal border of 

 each lamina is nearly straight, and terminates at each end in a process 

 or cornu^ the anterior of which (cornu craniale) is connected with the 

 end of the thyroid process of th« hyoid bone, while the posterior (cornu 

 caudale) articulates by a moveable joint with the cricoid cartilage. The 

 cranial cornu is much the more slender, and is separated from the rest of 



' \a.pvyi (larynx) [Gr.], a crier or bawler. 

 2 Lamina [L.], a jjlate. 

 ^ Cornu [L.], a horn. 



