80 TOPOGRAPHICAL AXATOMY OF THE 



two halves of the inaudible, where it is supported by the mylo-glossal 

 and mylo-hyoid muscles. 



In its anterior half the tongue is flattened dorso-ventrally, but 

 posteriorly it is so thickened that a transverse section presents a 

 triangMilar outline. The broadest part is close to the anterior extremity. 



It is customary to divide the tongue into three parts. The main 

 mass is known as the body (corpus linguaj), the ti}) or apex (apex 

 linguae) is the blunt, free extremity, and may be .separated from the body 

 by an imaginary transverse line drawn on a level with the first premolar 

 tooth ; the root (radix linguae) is the fixed part that is connected by 

 muscles and mucous membrane to the mandible, hyoid bone, pharynx, 

 epiglottis and soft palate. While the body of the tongue possesses 

 three surfaces — dorsal and two lateral — sej^arated by rounded borders, 

 the tip, because of the aforementioned flattening, has only dorsal and 

 ventral surfaces bounded by thick, lateral margins. 



The term dorsum'^ linguoe is applied to that surface of the tongue 

 which, when the organ is at rest, is in contact with the hard and soft 

 palates. In some animals, e.g., the dog, the dorsum is divided longitud- 

 inally into two lateral halves by a median sulcus. This groove is 

 absent in the horse. 



The whole of the dorsum and lateral borders is thickly studded with 

 elevations of the mucous membrane, the lingucd pajnlld^' (papillae 

 linguales), of which four kinds can be distinguished, namely, filiform, 

 fungiform, vallate and foliate. The filiform^ yapilloi (papillse filiformes) 

 are most numerous, and occur over the whole of the dorsum and on the 

 borders of the tip. They are small, thread-like and soft, and produce 

 the characteristic velvety appearance of the tongue of the horse. The 

 hmgiforin'^ papilUe (papillaE- fungiformes), less numerous than the 

 filiform, occur principally on the tip and borders and on the lateral 

 surface of the body of the tongue. They are shaped somewhat like 

 mushrooms, and can be distinguished readily by their rounded form 

 and pale colour. The vallate^ papilla', (papillae vallatse) are two in 

 number, and occur on the posterior part of the dorsum, one on each side 

 of the middle line, about 2'5-3 cm. apart. Each vallate papilla is large, 

 with a slightly constricted base and a flattened tubercular crown that 

 reaches a little above the general level of the mucous membrane 

 Around each papilla there is a circular fossa with an outer wall known 

 as the vallum. Occasionally there is a third vallate papilla, of smaller 

 size, placed in the middle line behind the other two. The foliate ^ 

 1 Dorsum [L.], the back. 2 PapiUa [L.], a iiipijle. 



3 Filum [L.], a thread. Forma [L.], form. ■> Fungus [L.], a mushroom. 



^ Vallatiis [L.], walled {vallum, a wall, rampart). 

 ^ Foliatus [L.], leaved {folium, a leaf). 



