DIGESTION OF FOOD: THE MOUTH 85 



mouth on the way to the stomach must pass over the upper 

 end of the windpipe. 



There are, therefore, seven openings into, or out of the 

 pharynx, all of which may be closed. The large passage from 

 the mouth may be closed by the tongue, the soft palate and the 

 pillars of fauces, all of which contain muscles; the Eustachian 

 tubes can be closed by muscles going around the tubes and by 

 the pressure of surrounding tissues; the glottis, by a lid-like 

 door, the epiglottis, which drops back over the opening when 

 anything is swallowed; and the oesophagus may be closed 

 through the contraction of muscles which pass circularly 

 around it. The entrance from the nose passages is less per- 

 fectly shut off than the others and less often; but it can be 

 closed by the raising of the curtain-like soft palate and the 

 general contraction of the muscles in the upper part of the 

 pharynx. One or the other of these openings may be closed ac- 

 cording to whether food or air is passing through the cavity. 



DISEASES OF THE MOUTH AND THROAT 



Tonsilitis. We have already noticed that the mouth usually 

 contains microscopic germs, called bacteria. Ordinarily these 

 do no harm, but occasionally bacteria of a more malignant 

 type get into the mouth and produce trouble. 

 They sometimes attack the tonsils or the* roof 

 and walls of the mouth and throat, causing 

 inflammation; the result is first noticed as a 

 sore throat, which may merely have an appear- FIG. 44. 

 ance of redness that soon disappears. If the BACTERIA 

 throat is covered with white patches, however, (STREPTO- 

 and the tonsils are swollen and painful, the 



Found in 



trouble is called tonsilitis; Fig. 44. This is cases of ton- 

 accompanied by fever and a general feeling of silitis< 

 illness; but it is not likely to be serious, and with proper treat- 

 ment will soon pass away. If the inflammation becomes still 

 greater, and the surrounding tissues are distended with pus, 



