THE TONGUE, 1 05 



tube, and swallowed after as little contact with the teeth 

 as may be possible. 



Many foods if kept in the warm moist mouth, decom- 

 pose and give rise to acids: the teeth should therefore 

 be thoroughly cleansed twice daily, with a soft tooth- 

 brush and tepid water. Finely powdered chalk or a 

 little soap may be placed on the brush with advantage, 

 as they counteract any acids which may be present. The 

 enamel is not so easily attacked as the deeper parts of a 

 tooth; but once the enamel is injured, the dentine is apt 

 to decay rapidly. Small cavities in the enamel are not 

 easily discovered unless they are on the outer side of the 

 tooth. Remnants of food collect in them and, making 

 acids, rapidly eat away the tooth. The teeth should 

 therefore be thoroughly examined by a dentist two or 

 three times a year, and all cavities filled. 



13. The Tongue (Fig. 60) is endowed not only with a 

 delicate sense of touch, but is the chief organ of the 

 sense of taste. Being highly muscular and very mov- 

 able, it also plays a great part in guiding food inside the 

 mouth, so as to push it between the teeth until it is 

 properly chewed, and then to drive it on into the 

 pharynx to be swallowed. As an organ of taste, we shall 

 study the tongue later (Chap. XXL). 



14. What a "Furred Tongue" Indicates. In health the 

 mucous membrane covering the tongue is moist, covered 

 by little " fur" and, in childhood, of a bright red color. 

 In adults, the natural color of the tongue is less red, ex- 

 cept around the edges and at the tip. When any part of 



13. Of what is the tongue the chief organ ? What muscular work 

 does it perform ? 



14. What is said of the covering of the tongue ? Color? Indica- 

 tions of disordered digestion ? 



