316 A YEAR IN SCIENCE 



repaid for any care he may give his teeth. They should 

 be carefully brushed at least twice a day. It is well 

 occasionally to use a soft powder. A mild antiseptic 

 mouth wash is also beneficial. The teeth should be 

 inspected by a dentist once or twice a year. 



The tongue. The tongue is a muscular organ 

 attached at the back to the floor of the mouth. On its 



upper surface are .numerous 

 elevations of different sizes. 

 These are called papillae ; in 

 them are located the nerves of 

 taste. In what form must a 

 substance be in order to taste 

 it? 



Salivary glands. In the 

 mouth there are two secre- 



Fig. 153. The tongue. ,. ,, 



membrane, and saliva from the salivary glands. There 

 are three pairs of salivary glands. Two of these 

 glands, the parotid (Greek meaning, "beside the ear") 

 are located in front of and below the ear. These are 

 the glands which swell in the disease known as the 

 mumps. From the parotid gland on each side a tube, 

 the duct, opens on the inside of the cheek opposite the 

 upper second molar tooth. 



The other two pairs of glands lie in the floor of the 

 mouth. These are the sub-maxillary (Latin, sub means 

 beneath, and maxilla means jawbone) and the sub- 

 lingual (Latin, sub means beneath, and lingua means 



