202 THE ANATOMY OF THE HORSE. 



a number of transverse or slightly oblique ridges. The ducts of small 

 mucous glands open into the furrows between these ridges, and gustatory 

 bodies are present in the mucous membrane which lines the furrows. 



The Sublingual Ridge. — This is a longitudinal elevation of the mucous 

 membrane at the floor of the mouth, on each side of the fixed portion of 

 the tongue. It is caused by the underlying sublingual salivary gland, 

 whose ducts open on the summits of little tubercles which stud the ridge- 



The Barbs. — These are two flattened, leaf-like papilke situated on the 

 inferior part of the floor of the mouth, one on each side of the freenum 

 lingua?. Wharton's duct — the duct of the submaxillary gland — dis- 

 charges itself by a minute opening on the summit of the barb. 



Structure of the Tongue. The tongire possesses a mucous covering, 

 a collection of mucous glands, a median fibrous cord, muscles, nerves, 

 and connective-tissue. 



Mucous Membrane of the Tongue. — This has already been partly 

 noticed. Like the rest of the lining membrane of the mouth, it has 

 a stratified squamous epithelium. It is intimately adherent to the 

 subjacent structures. It is thickest on the dorsum of the tongue, where 

 it is harsh and wrinkled. On the sides and posterior surface of the 

 tongue it is thin and smooth. 



The Lingual Fibrous Cord. — This is a fibrous cord extending along 

 the middle line of the dorsum of the tongue, immediately beneath the 

 mucous membrane. With a sharp scalpel incise the tongue along this 

 line to the depth of half an inch or more, beginning the incision behind 

 the circumvallate papillae, and terminating it in the free portion of 

 the tongue. This will expose the cord in its entire length. It is a 

 little less in thickness than a goose quill. It begins between the two 

 large circumvallate papillae, and it terminates towards the junction of 

 the free and the fixed portion of the tongue, being about seven inches 

 in length. 



Lingual Glands. — These are aggregated as a thick layer under the 

 mucous membrane at the upper part of the dorsum. The mucus which 

 they secrete coats the bolus of food as it passes through the fauces. 

 They are of the racemose type, and their ducts open on little tubercles 

 of the mucous membrane. 



Directions. — The mucous membrane is to be raised from the sub- 

 lingual gland and the sides of the tongue. It is convenient to describe 

 the gland here, although it is not a part of the tongue. 



The Sublingual Gland (Plate 30 and Fig. 23, 3). This, the smallest 

 of the salivary glands, is placed at the floor of the mouth, and at the 

 side of, rather than under, the tongue. It extends from the level of 

 the 5th molar tooth to the symphysis. It is in contact outwardly with 

 the mylo-hyoid muscle. Inwardly it is related to the stylo-glossus, 

 genio-glossus, and genio-hyoideus muscles, to Wharton's duct, and to 



