172 DISSECTION OF THE DOG 



raphe, which ends in front at a four-sided incisor papilla (papilla incisiva), 

 divides the surface into two lateral halves. Each half is raised into some 

 nine or ten curved transverse palatine folds (plicae palatinae transversse) , each 

 with its convexity turned forwards. The whole surface is covered with small, 

 low, blunt papillae. 



Flooe of the mouth. — When at rest, the tongue forms the floor of the 

 proper mouth cavity, but the term ' floor of the mouth ' is commonly used 

 to express a narrow area exposed when the tongue is raised. 



Continuation of the mucous membrane from the inner surface of the man- 

 dible to the tongue results in a degree of fixation of the greater part of this 

 organ. In the anterior part of the mouth, however, the disposition of the 

 mucous membrane permits of a greater amount of freedom. If the free portion 

 of the tongue be raised, a prominent median fold of mucous membrane, the 

 frcenulum of the tongue (frsenulum linguae), is disclosed, as is also the rudi- 

 mentary, flattened elevation, the sublingual caruncle (carunculus sublingualis), 

 on which open the ducts of the submaxillary and aboral sublingual salivary 

 glands. In the narrow groove between the tongue and the mandible are the 

 openings of the smaller sublingual ducts. 



Lingua. — The tongue is an organ concerned in mastication, deglutition, 

 and taste, and consists mainly of a mass of muscular tissue partially covered 

 with mucous membrane. In its anterior half the tongue is very decidedly 

 flattened, but posteriorly it is so thickened that a transverse section presents 

 a triangular outline. The broadest part of the organ is within a short distance 

 of the anterior extremity — roughly on a level with the first maxillary premolar 

 tooth. The main mass of the tongue is known as the body (corpus linguae) ; 

 the tip (apex linguae) is the blunt free extremity ; and the root (radix linguae) 

 is that part which is attached to the hyoid bone and the mandible. 



Dorsum linguae. — The term dorsum is applied to that surface of the tongue 

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

 The dorsum is divided longitudinally into two lateral halves by a groove 

 (sulcus medianus linguae), shallow towards the tip, but becoming much deeper 

 as it proceeds backwards. The whole of the dorsum is thickly studded with 

 elevations of the mucous membrane, the lingual papillae (papillae linguales), 

 of which five kinds can be distinguished, namely, filiform, conical, fungiform, 

 vallate, and foliate. 



The filiform papillae (papillae filiformes) are much the most numerous and 

 occupy the greater part of the dorsum. In the anterior half of the tongue they 

 are small, but posteriorly they become larger and finally merge into the next 

 group. The conical papillae (papillae conicae) are arranged in rows — as, indeed, 

 are all the lingual papillae — running backwards and towards the median groove. 

 Each elevation is sharply pointed and directed backwards. It will be noted 

 that the conical papillae are continued somewhat beyond the posterior limits 

 of the tongue. 



