470 THE ANAT03IY OF THE HORSE 



dry it is moistcncil, so as to render it fit for respiration. Tlie frontal, 

 {ptlnnoidal, splicnoidal and maxillary sinuses also open into these fossae, 

 the -whole of them being lined by a continuation of the Schneiderian 

 membrane. 



THE LARYNX 



Immediately ueiiixd and below the nasal cavities is the larynx, which 

 serves the double purpose of acting as a portal to the inspired air, and 

 of forming the few vocal sounds uttered by the horse. It consists of five 

 cartilages, united together by ligaments, and moved by a number of deli- 

 cate muscles. It is lined with a fine mucous membrnne, and is supplied, 



J 



FiQ. 73.— Profile View of the Os Hyoides and Larvnx. 



1. Lateral plates of the thyroid cartilage. 6. Spur jirocess, or ai>pendix. 



2. Ei'iglottis. " 7. Shorthorn. 



8. Thyro-livoid membrane. S. Long horn of the os hyoides. 



4. Boily of the tliyroid cartilage. 9. 9. 9. 0. Cartilaginous rings of the trachea. 



5. Branch of the body of the os hyoides. 10. 10. 10. Membranes connecting these rings. 



like all other parts of the body, by its proper vessels and nerves. It is 

 suspended from the os hyoides, or bone of the tongue, by a strong but 

 thin membrane, and terminates posteriorly in the trachea, or air-tube 

 loading to the lungs. 



The thyroid cartilage (^vpcos, a shield, elSo?, like) is composed of two 

 lateral plates, each presenting the form of an oblique-angled parallelogram, 

 joined together in front, and separated by a considerable bpace behind, 

 which is occupied by the cricoid cartilage. The point in front which 

 corresponds with the pomum Adami in man, is called the body. The 

 posterior angles of the lateral plates are each terminated by a prolongation, 

 called a cornea or ala — the two superior being united by ligaments to the 

 OS hyoides, and the two inferior to the cricoid cartilage. In the upper 

 part of the anterior angle is fixed the epiglottis, by means of the union 

 called amphiarthrosis. 



The cricoid cartilage (^piKos, a ring, €1805, like) is a complete ring, but 

 it is much deeper behind than before. It is somewhat depressed from side 

 to side, especially in those horses which are deficient in wind. On the 

 upper edge behind it has two rounded surfaces, which articulate with the 



