WASTE AND REPAIR FOODS g/ 



7. Give a list of animal and vegetable food-substances, and classify them 



according to their chemical composition. 



8. How would you obtain starch and gluten from wheat flour ? 



9. Compare the chemical composition of starch and fat. 



10. What are the chief mineral constituents of our foods? Describe the 



composition of each. 



1 1. What would be the disadvantage of feeding on bread or meat alone ? 



12. Explain clearly why it is better to make use of a mixed diet of bread and 



meat. 



1 3. What is a model food ? Describe the composition of one such food. 



4. Why are nitrogenous foods called tissue-formers, and non-nitrogenous foods 

 heat-producers ? State any objections you may have to this method of 

 classification. 



LESSON XVI. 



THE TEETH AND MASTICATION. 



EACH tooth has a crown, a neck, and a root consisting of one or 

 more fangs The crown is the part which protrudes beyond the 

 gum into the mouth. The neck is that slightly constricted portion 

 which is embraced by the gum ; and the fang or fangs include all 

 that part of the tooth which penetrates into the jaw-bone. 



If we examine our teeth we shall notice that they vary much 

 in general form Those in the front of each jaw are provided 

 with sharp, chisel-like edges, and are consequently well adapted 

 for biting or cutting : these are called the incisors (Lat. incido, I 

 cut). Next to these, on each side, is a single tooth of about the 

 same size, which has a somewhat pointed crown. This is called 

 the canine or dog tooth (Lat. canis, a dog), because its position 

 in the human skull corresponds with that of the long, conical, 

 tearing tooth in the skull of the dog and other carnivorous (Lat. 

 caro, flesh ; and voro, I devour) or flesh-eating animals. The 

 human canine tooth may also be said to slightly resemble that of 

 a carnivorous animal in general form, inasmuch as its summit is 

 more or less conical. Beyond these canine teeth on either side 

 is a pair of premolars or bicuspids (Lat. bis, twice ; and cuspis, a 

 pointed extremity), so called because each has two cusps or ridges 

 on the top of the crown, separated by a furrow. Beyond these 

 again are larger teeth, each possessing two or more fangs, and 

 having a very broad and irregular surface well adapted for the 

 grinding of foods ; hence these teeth are called the molars (Lat. 

 mola, a mill). 



A child of about six years possesses twenty teeth, called the 

 temporary or milk teeth. These consist of four incisors in the 

 front of each jaw, a single canine tooth on each side of these in- 

 cisors, and a pair of molars on each side beyond the canines. At 



