882 THE ORGANS OF SENSE. 



G-lands of the Tongue. The tongue is provided with mucous and serous 

 glands and lymphoid follicles. 



The mucous glands are similar in structure to the labial and buccal glands. 

 They are found all over the surface of the mucous membrane of the tongue, 



especially at the back part, behind 

 the circurnvallate papillae, but also 



-Bristles in Gland at tne a P ex an(1 marginal parts. 

 Ducts. [ n connection with these glands a 



_ Gland of Bland in special one has been described by 



Jfttn/R. -fi, ,. 1 TVT 1 T 1 



J31andm and JNuhn. It is situated 

 near the apex of the tongue on 

 either side of the frsenum, and is 

 covered over by a fasciculus of 

 muscular fibre derived from the 

 Stylo-glossus and Inferior lin- 

 gualis. It is from half an inch 

 to nearly an inch long and about 

 the third of an inch broad. It 

 has from four to six ducts, which 

 open on the under surface of the 



Lingual Nerve. apex. 

 FIG. 519. Under surface of tongue, showing position and Lhe SCTOUS (/lands OCCUr Only 



relations of gland of Blandin and Nuhn. (From a prepara- a t the back of the tongue in the 

 tion in the Museum of the Royal College of Surgeons.) 



neighborhood ot the taste-goblets, 



their ducts opening for the most part into the fossae of the circumvallate papillae. 

 These glands are racemose, the duct branching into several minute ducts, which 

 terminate in alveoli lined by a single layer of more or less columnar epithelium. 

 Their secretion is of a watery nature, and probably assists in the distribution of 

 the substance to be tasted over the taste-area (Ebner). 



The Lymphoid Follicles. The lymphoid tissue is situated, for the most part at 

 the back of the tongue, between the epiglottis and the circumvallate papillae, and 

 is collected at numerous points into distinct masses known as lymphoid follicles. 

 Here and there in this situation are depressions in the mucous membrane, 

 surrounded by nodules of lymphoid tissue, similar to the structure found in the 

 tonsil : into them open some of the ducts of the mucous glands. 



The fibrous septum consists of a vertical layer of fibrous tissue, extending 

 throughout the entire length of the middle line of the tongue, from the base 

 to the apex, though not quite reaching the dorsum. It is thicker behind than 

 in front, and occasionally contains a small fibro-cartilage about a quarter of 

 an inch in length. It is well displayed by making a vertical section across the 

 organ. 



The Hyo-glossal membrane is a strong fibrous lamina which connects the 

 under surface of the base of the tongue to the body of the hyoid bone. This 

 membrane receives, in front, some of the fibres of the Genio-hyo-glossi. 



Vessels of the Tongue. The arteries of the tongue are derived from the lingual, 

 the facial, and ascending pharyngeal. The veins of the tongue accompany the 

 arteries. 



Muscles of the Tongue. The muscular fibres of the tongue run in various 

 directions. These fibres are divided into two sets, Extrinsic and Intrinsic. 



The Extrinsic muscles of the tongue are those which have their origin external 

 to it, and only their terminal fibres contained in the substance of the organ. They 

 are the Stylo-glossus, the Hyo-glossus, the Palato-glossus, the Genio-hyo-glossus, 

 and part of the Superior constrictor of the pharynx (Pharyngo-glossus). 



The Intrinsic muscles are those which are contained entirely within the tongue 

 and form the greater part of its substance. Both sets have been already described 

 (page 415). 



The lymphatic vessels from the tongue pass to one or two small glands situated 



