DIGESTION AND ABSORPTION 



355 



of the space back of the soft palate is called the pharynx, or throat 

 cavity. From the pharynx lead off the gullet and windpipe, the 

 latter placed ventral to the former. The lower part of the buccal 

 cavity is occupied by a muscular tongue. Examination of its 

 surface with a looking-glass shows it to be almost covered in places 

 by tiny projections called papillce. These papillae contain organs 

 known as taste buds, the sen- 

 sory endings of which deter- 

 mine the taste of substances. 

 The tongue is also used in 

 moving food about in the 

 mouth, and in starting it on 

 its way to the gullet, while it 

 plays an important part, as 

 we know, in speaking. 



The Teeth. In man the 

 teeth, unlike those of the frog, 

 are used for the mechanical 

 preparation of the food for di- 

 gestion. Instead of holding 

 prey, they crush, grind, or tear 

 food so that more surface may 

 be given for the action of the digestive fluids. The teeth of man 

 are divided, according to their functions, into four groups. In the 

 center of both the upper and lower jaw in front are found eight 

 teeth with chisel-like edges, four in each jaw ; these are the incisors, 

 or cutting teeth. Next is found a single 

 tooth on each side (four in all) ; these have 

 rather sharp points; they are the canines; 

 look for them in a cat or dog. Then come 

 two teeth on each side, eight in all, called 

 premolars. Lastly, the flat-top molars, or 

 grinding teeth, of which there are six in 

 each jaw. Food is caught between irregular 

 Section of a tooth : a, projections on the surface of the molars and 



enamel ; 6, dentine ; crushed to a pulpy mass. 

 c, pulp cavity contain- 

 ing blood vessels and Internal Structure of a Tooth. If a tooth is 

 nerves; d, cement. cut lengthwise, it is found to be hollow; this 



Teeth 



j, inri.-ors; c, canine; p, premolars; 

 TO, molars. 



