ALIMENTARY CANAL AND ITS APPENDAGES 403 



most numerous and smallest, are scattered all over the dorsum of 

 the tongue except near its base. Each is a conical eminence 

 covered by a thick horny layer of epithelium. It is these papillae 

 which are so highly developed on the tongues of Carnivora, and 

 serve them to scrape bones clean of even such tough structures as 

 ligaments. 



In health the surface of the tongue is moist, covered by little 

 "fur," and in childhood of a red color. In adult life the natural 

 color of the tongue is less red, except around the edges and tip; a 

 bright-red glistening tongue being then, usually a symptom of 

 disease. When the digestive organs are deranged the tongue is 

 commonly covered with a thick yellowish coat, composed of a little 

 mucus, some cells of epithelium shed from the surface, and numer- 

 ous microscopic organisms known as bacteria; and there is fre- 

 quently a "bad taste in the mouth." The whole alimentary 

 mucous membrane is in close physiological relationship; and any- 

 thing disordering the stomach is likely to produce a "furred 

 tongue." 



The Salivary Glands. The saliva, which is poured into the 

 mouth and which, mixed with the secretion of minute glands em- 

 bedded in its lining membrane, moistens it, is secreted by three 

 pairs of glands, the parotid, the submaxillary , and the sublingual. 

 The parotid glands lie in front of the ear behind the ramus of the 

 lower jaw; each sends its secretion into the mouth by a tube known 

 as Stenson's duct, which crosses the cheek and opens opposite the 

 second upper molar tooth. In the disease known as mumps* the 

 parotid glands are inflamed and enlarged. The submaxillary 

 glands lie between the halves of the lower j aw-bone, near its angles, 

 and their ducts open beneath the tongue near the middle line. The 

 sublingual glands lie beneath the floor of the mouth, covered by 

 its mucous membrane, between the back part of the tongue and 

 the lower jaw-bone. Each has many ducts (8 to 20) , some of which 

 join the submaxillary duct, while the rest open separately in the 

 floor of the mouth. 



The Fauces is the name given to the aperture which can be seen 



at the back of the mouth below the soft palate (Fig. 122), and 



leading into the pharynx. It is bounded above by the soft palate 



and uvula, below by the root of the tongue, and on the sides by 



* Parotitis, in technical language. 



