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The Organ of Taste

tongue, surface, buds and nerve


The Tongue and Soft Palate are the seat of the organ of taste, which consists, like that of touch, in a particular mode of nerve termi nation. The tongue is composed mainly of muscular fibres running in various directions, and freely supplied by nerves and vessels. It is covered by mucous membrane similar to that lining the mouth, which contains glands in the deeper layers. The surface of the mucous mem brane is thrown into irregular projections, called papillae, of various forms. The filiform pa pilla3 are very short, fine, hair-like processes, which are exceedingly numerous over the whole surface. The fungiform papilla; are broader and mushroom-shaped, and are scattered over the surface. They often project as red points when the rest of the tongue is white and furred. The circumvallate papillae are the largest of all, and the least numerous. They are so called because consisting of a fungiform papilla sur rounded by a fold of the mucous membrane. They present the appearance of being walled round. They are found near the back of the tongue, being ranged in two lines, passing from a point in the centre of the surface towards the sides. There are only about a dozen of them altogether. The papillte all contain twigs of vessels and branches of nerves, and are covered by epithelial cells. In the circumvallate papillm

are peculiar structures called taste buds. Fig. 171 shows a section of such a papilla, in which A is the centre and la B sections of the surround ing fold. A trench is seen to separate the centre from the surrounding fold, and at the aides of the central papillae, in the deep parts of the trench, are a number of flask-shaped bodies (T T). These are the taste buds. They are formed of stave-like epithelial cells, repre sented in it of the figure. In the inside of the buds are finer cells, represented at tn. The mouths of the buds open into the trench. The taste bodies are connected with nerve-fibres, and it is supposed they are peculiar adaptations of epithelium, readily excited by sapid sub stances and transmitting the impression along the connected nerve.

The tongue is supplied with sensory fibres by two nerves, the glosso-pharyngeal, a branch of the eighth cranial nerve (p. 152), and a branch of the fifth cranial nerve (p. 151)—the gustatory branch. The former confers taste on the back part, and the latter on the front part of the tongue. Branches of the former also pass to the soft palate and neighbouring parts, and confer taste on it.