[Illustration: Fig. 134. A view of one side of the neck, showing the nerves of the tongue. 1, A fragment of the temporal bone. 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, Muscles of the tongue, fauces, and neck. 5, The tongue. 13, The common carotid artery. 14, The jugular vein. 15, The external carotid. 16, The internal carotid. 17, The gustatory branch of the fifth pair of nerves. 20, The glosso-pharyngeal nerve. 21, The hypo-glossal, or the muscular nerve of the tongue. 24, The pneumogastric nerve. 25, The facial nerve.] -=-=-=-=-=-=-=-=-=-=-=-= 868. What is the appearance of the surface of the tongue? Explain fig. 134. -=-=-=-=-=-=-=-=-=-=-=-= 868. The surface of the tongue is thickly studded with fine papillæ, or _vil´li_, which give the organ a velvety appearance. These papillæ are of three varieties. The first is situated near the base of the tongue. They belong to the class of mucous follicles. They are larger than the others, and are called _len-tic´u-lar_, from being shaped like a lens. These, together with the tonsils, (sometimes called the almonds of the ears,) secrete mucus, to lubricate the food in the act of deglutition. 869. The instruments of taste are the two other sets of papillæ. One set consists of small, oval-shaped bodies, which are scattered over the whole surface of the tongue. They give it a rough appearance, and are called the _fil´i-form_ papillæ. 870. The other set of papillæ is called the _fun´gi-form_. They are larger than the former, and consist of small, rounded heads, supported on short stalks, something in the shape of mushrooms, from which they derive their name. In the last two described sets of sensitive papillæ, the gustatory branch of the fifth pair of nerves ramifies. _Observation._ By applying strong acids, as vinegar, to the tongue, with a hair pencil, these points will become curiously lengthened. PHYSIOLOGY OF THE ORGANS OF TASTE. 871. TASTE is the sense which makes us acquainted with the savor of substances. When fluids are taken into the mouth, the papillæ dilate and erect themselves, and the particular impression excited is transmitted to the brain through filaments of the gustatory nerve. This sense is closely connected with that of smell. The pleasures derived from it are strictly sensual and corporeal, and contribute in no way to the expansion of the mind, like those of hearing and seeing. -=-=-=-=-=-=-=-=-=-=-=-= How many varieties of papillæ? Describe the first variety. What is the function of the lenticular papillæ? 869. Describe the filiform papillæ. 870. The fungiform papillæ? What nerve ramifies in the fungiform papillæ? How can these papillæ, or points, be seen? 871-875. _Give the physiology of the organs of taste._ 871. Define taste. -=-=-=-=-=-=-=-=-=-=-=-=