86 



HUMAN BIOLOGY 



, canine 



molars 



Chew or grind a piece of apple or bread. 



a. Describe the motion of the jaws in grinding food. 



6. In what part of each jaw are found the teeth that are 



used in grinding or chewing food (Fig. 28) ? 

 c. Describe the shape and grinding surface of these 



teeth. incLsora 



There are two kinds of 



cutting or biting 



teeth (Fig. 28), the 



incisors (Latin, in- 



cisum, from inddere /^Hf^feS't^l^ ~~~~ bicuspids 



= to cut into), and 



the canines (Latin, 



canis = dog, so- 

 called because they 



often resemble the 



pointed teeth of a 



dog). 

 There are also two kinds of grinding teeth, the bicuspids 



(Latin, bi = two -\-cuspis = point), and the molars 



(Latin, molaris = a millstone). 



a. (Optional.) Human teeth may be obtained from a dentist. 

 They should be cleaned by boiling them in strong caustic 

 soda solution, then in water. If possible, each student 

 'should examine and draw one of each of the kinds of 

 teeth named above. 



6. Determine by the use of a mirror the number of teeth 

 of each kind that you have and record the numbers 

 in a table in your notebook as follows : 



FIG. 28. Teeth in upper jaw. 



