146 DISSECTION OF THE TONGUE. 



SECTION XV. 



DISSECTION OF THE TONGUE. 



Directions. The tongue and larynx are to remain connected with each 

 other whilst the student learns the general form and structure of the 

 tongue. 



Dissection. The ends of the extrinsic lingual muscles that have been 

 detached on the right side may be shortened, but enough of each should 

 be left to trace it afterwards into the substance of the tongue. 



The TONGUE occupies the floor of the mouth, and is rather flattened, 

 with the larger end turned backwards. It is free over the greater part of 

 the surface ; but at the hinder part, and at the posterior two-thirds of the 

 under surface, it gives attachment to the muscles and the mucous mem- 

 brane which fix it to the parts around. 



The tip of the tongue (apex) touches the incisor teeth ; and the base, 

 which looks towards the pharynx, is attached to the hyoid bone, and is 

 connected likewise with the epiglottis by three folds of mucous membrane 

 a central and two lateral. 



The upper surface of dorsum is somewhat convex, and is received into 

 the hollow of the roof of the mouth; along the anterior two-thirds it is 

 divided into two equal parts by a median groove, which ends behind in a 

 hollow named foramen caecum. This surface is covered with papilla! over 

 the anterior two-thirds; but is smoother at the posterior third, though 

 even here the surface is irregular in consequence of projecting mucous 

 glands and follicles. The under surface, free only in part, gives attach- 

 ment to the mucous membrane, and to the different lingual muscles con- 

 nected with the hyoid bone and the jaw ; and in front of those muscles is 

 a fold of the mucous membrane named fraenum lingiue. 



The borders of the tongue are thick and round at the base of the organ, 

 where they are marked by vertical ridges and furrows ; but gradually be- 

 come thinner near the tip. 



Papillae. On the dorsum of the tongue are the following kinds of pa- 

 pillse; the conical and filiform, the fungiform, and the circumvallate. 



The conical and filiform, papillae are the numerous small projections, 

 like the villi on the mucous membrane of the small intestine, which cover 

 the anterior two-thirds of the dorsum of the tongue. Some of the papillae 

 (conical) are wider at their attached than at their free ends, and these arc- 

 most developed over the central part of the tongue. Others become longer 

 (filiform), especially towards the sides of the tongue. These papilla- un- 

 furnished with minuter papillae, and are provided at the tip with hair-like 

 processes of the epithelium. Towards their limit behind, as well as on the 

 side of the tongue, they have a linear arrangement. 



']?\\v funyiform papilla; are less numerous but larger than the preceding 

 set, amongst which they are scattered. They are wider at the free end 

 than at the part fixed to the tongue, and project beyond the other set ; 

 they arc situate mostly at the tip and sides of the tongue. They are 

 covered with small simple papilla;. 



The circumvallate or caliciform are fewer in number and larger than 

 the others, and are placed at the junction of the two anterior with the 



