THE SENSE OF TASTE. 153 



figure. They are quite large, and consist of a central projection of mucous 

 membrane, surrounded by a wall, or circumvallation, from which they 

 derive their name. 



The Taste Beakers, supposed to be the true organs of taste, are flask- 

 like bodies, ovoid in form, about 3-^ of an inch in length, situated in 

 the epithelial covering of the mucous membrane, on the circumvallate 

 papillce. They consist of a number of fusiform, narrow cells, and curved 

 so as to form the walls of this flask-like body; in the interior are elongated 

 cells, with large, clear nuclei, the taste cells. 



Nerves of Taste. The chorda tympani nerve, a branch of the facial, 

 after leaving the cavity of the tympanum, joins the 3d division of the 5th 

 nerve between the two pterygoid muscles, and then passes forward in the 

 lingual branches, to be distributed to the mucous membrane of the anterior 

 two-thirds of the tongue. Division or disease of this nerve is followed by 

 a loss of taste in the part to which it is distributed. 



The glosso-pharyngeal enters the tongue at the posterior border of the 

 hyo-glossus muscle, and is distributed to the mucous membrane of the base 

 and sides of the tongue, fauces, etc. 



The lingual branch of the trifacial nerve endows the tongue with gen- 

 eral sensibility; the hypoglossal endows it with motion. 



The nerves of taste in the superficial layer of the mucous membrane 

 form a fine plexus, from which branches pass to the epithelium and pene- 

 trate it ; others enter the taste beakers, and are directly connected with the 

 taste cells. 



The seat of the sense of taste has been shown by experiment to be the 

 whole of the mucous membrane over the dorsum of the tongue, soft palate, 

 fauces, and upper part of the pharynx. 



The Sense of Taste enables us to distinguish the savor of substances 

 introduced into the mouth, which is different from tactile sensibility. The 

 sapid quality of substances appreciated by the tongue are designated as 

 bitter, sweet, alkaline, sour, salt, etc. 



The Essential Conditions for the production of the impressions of 

 taste are (i) a state of solubility of the food ; (2) a free secretion of the 

 saliva, and (3) active movements on the part of the tongue, exciting pres- 

 sure against the roof of the mouth, gums, etc., thus aiding the solution of 

 various articles and their osmosis into the lingual papillae. Sapid substances, 

 when in a state of solution, pass into the interior of the taste beakers, and 

 come into contact, through the medium of the taste cells, with the terminal 

 filaments of the gustatory nerves. 

 K 



