. Human physiology. iorportion of the palate. On the under surface ofthe tongue the mucous mem-brane is smooth and thin,like that of the walls of themouth generally-; but itsupper surface is renderedrough and sensitive to tasteby a number of papillae whichare richly supplied with nerveterminations. The papillae of the tongueare large compared with thoseof the dermis ; they are alsoquite distinct from each smallest and most nu-merous of these are conicalor cylindrical in shape, andare called filiform (Lat. filum,a thread). Mixed with theseare a number of larger papillaecalled fungifor
. Human physiology. iorportion of the palate. On the under surface ofthe tongue the mucous mem-brane is smooth and thin,like that of the walls of themouth generally-; but itsupper surface is renderedrough and sensitive to tasteby a number of papillae whichare richly supplied with nerveterminations. The papillae of the tongueare large compared with thoseof the dermis ; they are alsoquite distinct from each smallest and most nu-merous of these are conicalor cylindrical in shape, andare called filiform (Lat. filum,a thread). Mixed with theseare a number of larger papillaecalled fungiform (Lat,.fungus,a mushroom) on account oftheir resemblance in form tocertain of the fungi. Theyeach consist of a round andbroad extremity supported ona narrower stalk, and areeasily distinguished from the others by their deep red the back of the tongue there are from seven to twelve verylarge papillae arranged in two rows obliquely, so as to form theletter V with the point turned backwards. These are termed. Fig 179.—The Upper Surface of theHuman Tongue. 198 ELEMENTARY PHYSIOLOGY the circumvallate papillae (Lat. circum, around ; and vallum, arampart) because they are each surrounded by a kind of wall orrampart. All the papillae are richly supplied with blood-vessels and nerves. Thenerve fibres are obtained from two sources—the glossopharyngeal and the fifthpairs of cranial nerves. The former nerves supply the back of the tongue andof the palate, while the latter send their fibres to the middle and tip of thetongue. It is probable that both these nerves are nerves of taste, although theyappear to be dissimilar in their functions. It is easy to prove, for instance,that different portions of the mucous membrane of the tongue and palatepossess different powers. Sweet and salt tastes are perceived more readily atthe tip than at the back of the tongue. Sugar may be brought into contactwith the back of the tongue or palate without any taste being detected, at leastuntil t
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