THE TONGUE 



335 



of the mucous membrane passes from upper to lower jaw. This is termed the pHca 

 pterygomandibularis: it contains a ligament of like name. 



The isthmus faucium is the orifice of communication between the mouth and 

 the pharynx. It is bounded above by the soft palate, below by the root of the 

 tongue, and laterally by the anterior pillars of the soft palate. It is long, relatively 

 small, and not very dilatable in the horse, and is closed by the soft palate under 

 normal conditions, except dur- 



Trachea 



ing deglutition. 



Thyroid gland' 



Foliate papilla 



Vallate papillce 



Crico-arytenoid- 

 eus posterior 



Arytenoideus 



Arytenoid carti- 

 lages 



Vocal cord 



Adilus laryngis 

 Epiglottis 



Tonsil 



Adenoid tissue of 

 root of tongue 



Anterior pillar of 

 soft palate (cut) 



Dorsum linguoe 



THE TONGUE 



The tongue (Lingua) is 

 situated on the floor of the 

 mouth, between the rami of 

 the mandible, and is sup- 

 ported mainly in a sort of 

 sling formed by the mylo- 

 hyoid muscles. Its posterior 

 portion, the root (Radix 

 linguae), is attached to the 

 hyoid bone, soft palate, and 

 pharynx. Only the upper 

 surface of this part is free, 

 and slopes downward and 

 backward. The middle por- 

 tion, the body (Corpus linguae), 

 has three free surfaces. The 

 upper surface or dorsum (Dor- 

 sum linguae) is rounded. The 

 lateral surfaces are nearly flat 

 for the most part, liut an- 

 teriorly become rounded and 

 narrower. The lower surface 

 is attached to the mandible. 

 The apex or tip (Apex linguae) 

 is free, spatula-shaped, and 

 presents superior and inferior 

 surfaces and a rounded border. 



Structure. — The tongue 

 consists of: (1) The mucous 

 membrane; (2) the glands; 

 (3) the muscles. 



The mucous membrane 

 (Tunica mucosa linguae) ad- 

 heres intimately to the subjacent tissue, except on the lower part of the 

 lateral surfaces of the body and the under surface of the tip. It varies 

 considerably in thickness. On the dorsum it is very thick and dense. 

 Underneath this portion there is a dense fibrous cord, which extends medially 

 a distance of five or six inches forward from the vallate papillae. On 

 the sides and under surface of the tongue the membrane is much thinner and 

 smooth, and can more readily be dissected off the muscular tissue. From 

 the under surface of the free part of the tongue a fold of the mucous membrane 

 passes to the floor of the mouth, forming the frenum linguae. This contains the 

 anterior edges of the genio-glossi muscles. Posteriorly a fold passes on each side 



Apex linguce. 



Fig. 241. — Tongue of Horse, Dorsal Aspect. 



